They've already done paper cutout collections of fashion designs of the 1920s, 1930s and 1950s, so it is no surprise that the latest entry from Dover Publications is "Great Fashion Designs of the Forties." The clothes choices are good ones, particularly for those who remember their mothers or grandmothers wearing Maurice Rentner or Patullo-Jo Copeland suits, Molyneux, Balenciaga and Traina-Norell costumes or evening dresses by Adrian or Hattie Carnegie -- or if you wore them yourself. Part of the charm is that the hair, the hats, the gloves and shoes are all appropriate, and even the paper doll is wearing the boned corset and brassiere of the day.

The book includes the most celebrated suit of the decade, Dior's New Look, which marked the end of fabric restriction and the introduction of the nipped waistline and the full-skirt style.

If the publishers hurry and bring out a book on the 1960s, they will catch up with today's other great influence on fashion, the miniskirts and short chemises.

Lucci on Legs

Susan Lucci doesn't feel any less a scoundrel if she wears a short skirt or a long one as Erica Kane, television's most enduring bitch, in "All My Children." Although she was wandering around Georgetown early one morning recently in a white leather miniskirt and a white cotton Ralph Lauren sweater, both her on-and off-stage wardrobes are almost equally divided for the moment, at least. "I'm not decided on short skirts," she admitted. "There's a place for short and snappy and sexy, but I'm partial to the long and graceful skirts as well . . .

"As most women, I like to have men look at my knees," Lucci said. "But I also like independence and not being told what to wear."

At the moment she's shortening an Emanuel Ungaro dress for television, and others for her personal wardrobe. Designers overlap but not the actual clothes. Besides the Ungaro, in Lucci's closet at home and her wardrobe for the show are clothes by Valentino and Yves Saint Laurent.

Lucci, who was in Washington to promote the fragrance appropriately named Scoundrel, says that although "All My Children" continued during the Iran-Contra hearings -- "We were the lunch break show" -- she watched the hearings full time. "Real life is always better than fiction. It was better than any soap."

Sew In the Know

Sew what you want (as long or short as you want) this fall with the help of sewing classes in the Washington area. The Washington Post will list sewing classes in the Style section the first Sunday in September. If you offer sewing classes to the public, kindly send information about such classes, including times, fees and skills required to Martha Dailey, Fashion Department, The Washington Post, 1150 15 St. NW, Washington D.C. 20071.

Keeping Things in Proportion

"A petite can wear anything in the right proportion," says Louis Dell'Olio, designer for Anne Klein, which produces some of the best petite clothes around. "Take any regular size design, shrink it down and it will be perfect for someone short. It's not the style that makes the difference -- it's in the proportion."

Dell'Olio knows that women under 5 feet 4 often seek guidance, and he's providing just that in a newsletter, available by subscription, along with seasonal color brochures. "I learned my lesson about short women seeing how superbly dressed the Japanese women always are at the international fabric fairs in Europe. They wear everything with confidence and they look great -- because the proportion is right. They are never inhibited by style."

He is convinced that petites will be delighted with the new shorter skirts, which he is shipping at 22 inches, just at the knee, and shorter. "Short women will be relieved finally not have to shorten their skirts."

Notes de la Mode:

Viyachelsav Zaitsev, the Bill Blass of the Soviet Union, will market his clothes in the United States next month, according to the newspaper Soviet russia. According to the paper, the Soviet Fashion House, where Zaitsev is chief desinger, has contracted to supply 120 Soviet fashion designs for presentation in the United States in September. Raisa Gorbachev, wife of the Soviet leader, is a client of the house.

No one will doubt the origins of Bill Kaiserman, the American-born designer now working and living in Milan, after seeing his new collection. For next spring, Kaiserman has used the U.S. presidential seal on jackets and shirts with Kaiserman's name integrated into the design. The designer checked with his attorney and with customs and was told there was nothing illegal about using the seal. "It is the most beautiful seal that exists," says Kaiserman, "And since I am an American I wanted to relate (my clothes) to my background."

How many ways are there to tie a scarf? Grace Lee, f rom Hecht's creative merchandising department, knows dozens, but she concentrated on tying scarfs five or six ways in a demonstration for nurses at the National Cancer Institute. While only 30 or so nurses were free to attend the lecture, the program, organized by Arlene Berman, a clinical nurse at NCI, was videotaped to show to other nurses and patients. A Lancome makeup artist also gave makeup tips for those undergoing treatment.

What's making Washington retailers nervous these days? Conversations like this: Legendary San Francisco columnist Herb Caen repeated a conversation overheard at airport baggage carrousel in the San Francisco airport: "So how do you like Florence?" "Fine." "What did you buy there?" "Nothing, I do my shopping at Nordstrom's." (Nordstrom opens in the Washington area next March.)