Even with a 32t, the main pivot is still above the chain on my bike. But I like how it rides, and just leave the shock set with the least low speed compression damping, and still don't notice any Bob. I actually think the frame I have (it is a Hong fu fm058, which I believe is pretty much the same) is designed for a 34t. If I had a 50t rear cog, I certainly would be using a 34t chainring, and would probably run a little extra compression, and maybe look into getting a remote lockout. If you want the suspension as active as possible under power, and you plan to habitually use a lockout, you should go for the biggest chainring possible. These frames are somewhat copies of the Scott spark - Dunno if the main pivot is in the exact same position as the spark, but Nino schurter runs a 38t on his spark (he states it is mainly for reducing friction losses, but maybe he is also doing it to gain some traction on the rougher climbs).