The recommended props you mention sound about right for that engine on 10%.
I run an MDS40 on 10% and an 11x6 and it is very happy to fly my Gangster on half throttle. I have trihe a 10x6 but it HOWLS with that and gets quite hot, so you may seize / wear out your engine sooner. As for 30%, the highest I've seen used is 20% and that was in a DF model with a high performance engine. I would stick to 10%, any more is useless unless you really need that little extra power.
Sergeant.