He doesn't need to do that sleeve on the stock Rn bracket and poll, it's works just fine stock and gets hella tight with the 2 wrench method with decent bushings..., both boats here are run this way with no issues
If he wanted to take the time to trick it out then ya that's an improvement or could help with an unknown issue
For me the first step is inspect the bushings best you can while mounted and tighten the bolt with 2 wrenches, If it tightens ok now your done
For RRP I like your sleeve you made, if I add a spring to my RRP I'll try that