Yes that's right! Get the end cap for sure, I was thinking P3 sorry, that comes with all sections for all batt sizes.
Well, I've done some poking around on their site, and instead of the Zombie, I've decided on the Metallic Harlequin Green 2.5 (comes with FREE 18650 extension cap) for $29.95 + a Gold Zenkote 2.5 (with included extension cap for 18650) for $39.95. I think those will do me. Can't see needing to get a Classic at $49.95 + $8 for another extension ring...just to be able to use 18650 batteries in it, too. The Classic being VV + VW, plus coming with the flat top...doesn't really matter to me since I don't use big honkin' tanks anyway.
Adding those above to my Satin Silver 2.5 and the "snogard" of Dragons I got last month...I'll be done then with buying Provaris for my stash.