It's my understanding that Letrozole can cause hair loss due to increased DHT levels. Which I believe is the same way Test increases hair loss.

Would taking Letro while on T increase hair loss more so then just on the T alone?

I am assuming no, but a friend of mine swears he is experience more hair loss after switching from adex 1mg ed to letro 2.5mg ed (for gyno purposes) he's on moderate dose of test and has been for a while.