Custom a/c install: Tech question on dual parallel flow condensers
 

We are doing a couple cars destined for really hot climes. Both are pre 73 911's and both will be on R 134.
Both will NOT have the rear deck condenser. We are making custom gas tanks for them that allow a chamber under them for the condensers to sit in. The opening, for sake of discussion is 15" x 21".

A 1250 cfm fan will push thru air sourced from the battery box opening on the passenger side. The chamber will be well sealed so all the air has to go thru the condenser.
Parallel flow condensers are available in 14 x 21 so there is a fair amount of surface area. BUT i am worried that it's not enough. As there are no other condensers planned outside this chamber, would this be sufficient for 125 degrees ambient?

If i double stacked another condenser, again with the pusher fan , would the efficiency go up 25%, 35% 50%? Condensers are sure cheap enough and we are only talking some extra hose and fittings to put a second one on top of the first.

Edumacated comments please SmileWavy