Post pics and price. Saying "text for pics" ain't good enough. If you have a phone with a camera, get tapatalk and post the pics. I'm not looking to buy anything, but this should help your sell. JMO.
I would think the flow for a Cub is maxed out with the 6" filters (especially with 35 mm carbs), so anything bigger shouldn't make a difference. Do a WOT plug check to be sure it you're worried about it.
Yes. That happens pretty quick sometimes. On the bigger bore engines it looks like that immediately, and just gets worse.
If your ring end gap is in spec on those, I'd run them.
I'm looking for a website to order these from. I checked Grainger and a few others. Or maybe they are called something different? I found some called well nuts, but they are only threaded on one side.