how to bring and setup Custom controller in default 1st person Project??

Hi everybody,

I modified the 3rd person default BP added my own vehicle did many inputs and effects. Now I Migrate this asset to the default 1st person project and want the 1st person player to control this migrated 3rd person pawn(vehicle). Possessing works fine, but if I scale migrated 3rd Person Pawn(vehicle) the movement & the effects are all reduced to the default size.
Is there a way to uniform scale this vehicle??? or is there a systematic approach to bring custom characters and scale them in default 1st person project???

thanks in advance.