Actually I think it would be fully possible, but by the time you were done... It would be so modified that it wouldn't be classified as powder toy. After all, TPT's falling calculations are only meant for 1x1 pieces.
ace do you look specifically for "moving solids" posts and criticise them? never mind, though. at least you dont flame like SOME people... *cough*zolch111*cough*
@ozone If someone makes a moving solid thread and they get flamed, it is their own fault, there is a stickied thread labeled "What Not To Suggest". And for the millionth time Powder Toy is coded differently to games that have moving solids!