I've sold my cap so I can't try it, but HCigar has a kayfun clone that comes with a nano kit, and the nano-rings are a little taller than your standard nano rings that both you and I have in our pictures.. Considering the chimney is only slightly too long that small amount of added height from the mid-sized HCigar rings might allow you to use matching rings with the cap.
Unfortunately HCigar only offers the kit in a package along with the KFL, but I figured I'd let you know in case you wanted to try another configuration and were going to get another KFL in the future. I really wish they would sell the nano kit by itself because the rings and top cap are both really nice, I've got the top cap sitting on my authentic KFL with full size rings and it still makes it a bit smaller compared to the stock setup on the right.
