I have found that on plastic the buffing metalizer aluminum plate works best shot over bare plastic for the best results after buffing. Priming first gives a differ effect. For some reason it does not work the same on bare resin parts.
Isn't the X-7 the bottled paint? I believe they are a acrylic paint that would not be compatable with TS-13 clear coat. Please correct me if i'm wrong. I have used TS-13 for several years and never had a problem over the Tamiya and Model Master lacquers Also have used Mr. Hobby clear with no issues.
I am not using the 2 half style slicks, they just don't look right even cleaned up. The Polar Lights slicks have a back side insert that is side wall only.
I am seeing the split from the rim straight out to the tread area.
I was just taking one of them apart to check where the adhesive points were and it was where it started, has to be adhesive related. I also found that the rim was a tight fit in the tire which is probably contributing to the problem.
I'm tempted to try micro crystal clear or check out a vinyl adhesive, also using an exato blade to give just a little more clearance ( hopefully a slip in fit.