the new zen's do have a tighter fitting top cap, and those new top caps are for sale now (not sure i can post where in here though) if you dont want to buy a new one, JR has an awesome tutorial on how to fix that issue w/ o rings that he posted a while back and linked above... and yeah as had been stated before the zen SW is an awesome out of the house PV, I used one exclusively for my outside PV for months w/ no issues at all.
i totally get the thing about not wanting to have to modify your expensive PV once you get it, but the truth is, I have pretty much had to modify, or modified every single high end PV that I've owned, or have done it for freinds. (just a few examples: my modded SW: too many to list here, but i did that for fun, iHy: tubes not lining up correctly and having to sand them down, kick wont work w/out modifying the switch [not that i care or would ever use one, but hey, just putting that out there bc its supposed to work w/ one] paps and gus tele: replacing crappy hot spring w/ solid brass headless screw, GGTS: sand switch and axis to make it fire more consistently but still not happy w/ it, and removing all the burrs from and having to sand the tops of imeo's crap threading to get telescope to work, gone through two of those, and to get it to fit into a top tube or to get the stealth rethereader to fit on a ZAG, ProVari/ZAP: had to remove the paint and give a brushed finish bc it looked like it had been through a war after my gf used it for two weeks bc there is no media blast under the paint, nothing for it to stick or hold on to and it just chips off too easily, remove top peice to get it indexed w/ the wick on the ZAP, and remove the dumb satin finish on the ZAP beauty ring that doesnt match anything and sticks out like a sore thumb... etc. etc. and the list goes on)