my rear tires are 26.3" tall, the fronts are 25.9" tall.
i undertand what you mean by stretched when you say 235 on a 10" wheel... thats REALLY pulled/stretched in my book, lol. but my 255 up front on my 9" wheel recommended to me by my tire guy who sells/installs lots of tires for Mkiv's and i told him thats what this set was for. so the 255/35 is typical for a lowered mkiv, im sure. so, compared to your defniition of stretch, my tire would be "Square" for you. i should probably stick w/ the 255 since the sidewalls look tight. going wider would probably make the fronts square/mushroomed. in theory, i dont think id even want a square tire up front just for the sake of steering response.
i looked at my car again today, and it Should come down about an inch in the rear and over an inch up front to look decent. i do have quite a bit of clearance under the car itself, at least 6" from the pinch weld to the ground. if i go too low, i may have to change my side pipes.
i really like your idea of 285's all the way around. itd certainly make handling alot more neutral without having to tweak all your settings. you dont mean getting long long studs to go thru spacers and the wheels do you? that sounds kind of scarey. i saw a 1300hp mkiv shear the lugs on his welds at the track. he was running 1" spacers... craziest thing ever but i guess its too be expected. maybe itd be safe to run the stock studs, bolt on the spacers that have the second set of wheel studs and change out those studs for slightly longer ones.
speaking of spacers, since i didnt buy those 19's, i have 1" spacers that i dont think im giong to be using now... what the hell can i use these things on now? lol