First of all, comparing TeleFinder TCP transfer speeds to ftp speeds from a server in Hawaii is a diffcult exercise. Since we do not know the connection spped they have ( maybe its t1 vs our 56K ), or the number of users active on each server at a time.
With TCP/IP you have to share the base rate with each other user. so 56K gets used up pretty quick ( 2x28K, 4 x 14k and so on )
>Do you have an explanation for the low ISDN speeds?
Again, without experimenation we cannot make a judgement about a single file transfer.