I think keep your warranty valid must take precedence over the exterior look of your car?
Surely your car having the "stance" you like is not more important than knowing when you have a fault with the car you can just drop it in and have it repaired and possibly not pay more than your excess. (Provided the failed part is covered of course)
Personally I would not want to risk it. Sure they may not check/notice, but if they do its just going to mean they have a get out clause.