I have two Ivy rods. Both .187 44". Denny will make you a .187 rod with a 8-32 thread so you don't need to use an adaptor. Most .187 rods use a 5-40 thread because an 8-32 thread must be done very carefully. Denny can do it right. I also use a rod guide that fits the rod perfectly. I beleave my gunsmith uses the same rods.
Yes, jag selection. All 22 cal. jags (all I know of) are 8-32 thread. 17 and 20 cal jags are 5-40. To use most 20 cal. rods (.187) with a 22 cal jag you need an adapter. I have a few around somewhere but thats the point. Just something else you DON'T have to keep track of.
I shoot rimfire benchrest. IR50/50 and ARA. I use my .187 Ivy rods a lot. I switch from brush to different jags for different barrels. In three years the 8-32 thread hasn't been a problem.