Are you proposing using the stock top mount? The biggest reason to change intercooler for road racing when using water injection is to reduce pressure drop. The larger the core opening the more air it will flow with the least amount of pressure drop. The lower the pressure drop the less exhaust manifold back pressure the more power made for a given boost.
If you are using something like ECUTEK you can davance igntion timing in off boost transition to case the engine to acclerater quicker.
I would refer you to
www.bellintercoolers.com to compair flowsof different size and configurations of cores. Lowering the exhaust manifold backpressure for the same boost pressure is more power.
The short distance from turbo to intake valve is a big conderation. I would suggest Subarus top mount was more a design to prevent damage in WRC events and the like.
A good test for your current setup would be to logg intercooler discharge temps for an event and see if the intercooler is getting heat soaked.