Sorry to be late to the party, it's been a few weeks since this post came out.
I was surfing various forums / U-tubes this past week, can't remember exactly who. They had issues with the R4's and a 60" deck when turning left. The front left tire would rub on the deck (not the scalping wheels). Didn't happen when turning to the right if I remember correctly.
There are various opinions (pro & con) on OTT to adding spacers on the front wheels but I don't think it would help clear the deck while turning. I sure if I'm wrong I'll here about shortly. LOL
p.s. I personally would not add spacers to the front tires.