Definitely go up to an APC prop...Try the 11.5x4 as well as the other two that have been mentioned. If you're like me, you will like the 11.5x4 the most and think the other two are too big!

I never did any mods to my Extra Special and it was 4.2 lbs...I used light wheels, but that's about it. Yours can't be much more than that unless you built it with plywood...

I'd say try the different props and you will get some vertical. Also, move the CG back for those climbing flat spins...