i run different model/tier/size of tire in front and back. My Lynskey came with Conti Ultra Sports in 28mm, which had fine clearance on the fork, but rubbed under power in the back (real width measured at 31.6mm). Switching to a GP4K in 25mm in the back solved this problem (real width 28mm). Considering I figured this out after my first two rides, I wasn’t going to throw out a pair of perfectly fine and nearly new Ultra Sports, so for now I’ll continue running the OEM tire in the front, and keep the spare Gran Prix for the rear. given how little wear the front tire’s seen so far, I’m likely to go through the two GP4ks before I even go through one of the Ultra Sports (provided they don’t somehow get destroyed).
Use what ya got. That it works and you’re out riding matters more than anything else.