Power loss through a C4 trans

Run a search, and theres a lot of good information and debate on transmission power losses in the forums.

Yes the converter could play a part in it. I've seen a car go from a real tight converter, to a looser one, that picked up some time in the 60ft, only to not mph as well, and thus run pretty much the same times as he did with the tight unit.

We found about the same, 23-28 hp loss through a well built C-4
We also discovered the Gear Vendors guys were very close to boasting about only a minor loss in HP through their new Over drive units.
We added one to the same motor/C-4 combo & figures were
Before -365 hp
after GV install -360hp
For some reason torque was up 6% to 5800 rpm, never quite figured this out
GV advertises only a 1-5% parasitic loss & it seems they;re darn close!