RotoMax 1:60 Motor voltage ?

by Mike
(Grimsby England.)

I have a RC 9kg auw. 90" Seagull 40cc to 50cc Stuka plane.
I Installed a 1:60 RotoMax motor KV/RPM-231. P/Watts-2960. 80A max current.
Sugested prop-21x13 APC wide.
Spec says 10cell/37v battery.

Can I use 12s/44v battery with smaller propeller to keep the watts down ?
If so what would be the correct size propeller ?

Any other information, recomendations for the plane with the above motor would be appreciated.
I would like to avoid having to purchase another 4 5S 50000mAh batteries when I already have several 6s 50000mAh Lipos.

Thanks.