[7.470][QUESTION][OPEN] Downloads speeds cut in a third through proxy

When using the proxy, the speed I get downloading is greatly reduced.

I usually get around 1/1.2M d/l speeds and through proxy, I am getting consistent 300-400K

...should this be expected?

EDIT:  this is in Safari 4.0.2 on MAC OSX 10.5.8
EDIT:  looks like I am experiencing the dropped large files as I read in some other posts....