X-Shot Longshot Mod

Bought a LongXshot recently and instantly fell in love with its ergonomics and form factor. I enjoy the Skins line in general, but I wanted to personalize this blaster. And while I was at it, I changed some of the internals as well: 16cm of K25, a metal plunger tube, a 45cm aluminum barrel (from a Swift iirc) with a BCAR and lots of Lube to increase performance. I‘m satisfied with the performance now (sadly, no chrony for exact measurements), but the air seal is not perfect yet. I changed the O-Rings in the plunger assembly to slightly larger ones with Teflon tape underneath them, but somewhere, air is still leaking. Any recommendations on how I can further improve the air seal are highly appreciated! :)