Either that or export the huge models as .OBJ for scaling up with OBJaction Scaler. Or use a 3D format conversion program that incorporates a scaling ability, and scale the models down. Be aware that in 3D model conversion there is always a chance that you'll come across "interesting behaviour". To cut a logn story short, a lot of stuff fworks well but there are always the exceptions which confound you with bizzarre results. In particualt sometiems .3DS models "explode" when imported into another program. Persevere - there are solutions to many of the problems, though they mostly involve some work ;(