Im using a G6 Real in slot 1 and Ez 3 in 1 in Slot 2.
Works pretty well apart from two things:
1) You can only have one game on the EZ3in1 at a time (although you can swap out any time with GBA games stored on the G6 anytime..) but the swapping takes a few moments (sometimes up to a minute for big games).
2) Some games have to be patched using an app like gbata in order to save properly.
The alternative is a G6 lite i guess but its waaaay more expensive.