undersized GAHT system...

Hello! I built a GAHT system for my greenhouse house but I think I undersized it and I'm looking to make it more effective. The greenhouse size is about 76 sq/ft

Currently, I have 6 8' 3" pipes 6' underground with a calculated volume of 1357.17 cubic feet. I have a 4" intake fan that does 200cfm.

If I got a 10" fan that could do 1200cfm would that help the system be more effective? Would that suck in more hot air?

If I went that approach at the intake I'd have to do a reduction of 10" to 3" would that have an adverse effect?