Thank you both for your answer, the gimbal is a Hobbypower, bought on March on Amazon, and the expansion board is from gadgetextreme on Ebay, received yesterday.
Anyway, took the chance today and soldered them, then tested using 2.2b2 (fw that came on gimbal), unmounted and without motors, and so far works fine, didn't burn and GUI recognized both cards.
Was wondering why expansion card has two ground pins and the 2 axis board only 1 ground hole, would it be better to bridge the 2 grounds?
And another doubt is, don't know if 2 axis card is original or not, if it is not and I upgrade to 2.3b5 would this brick it?
If it is not an official supported alexmos card it will either not work after the uppgrade, or you wont be able to uppgrade at all. Anyway you can flash back the nulled firmware. Some report of it not working but many report it does. Its a gamble you have to make i guess.