[Digger]

<font color='#000080'>Gareth, I've replied to your PM.

As regards mixing and matching, you can do it with alomst any reg except Poseidons, and you also can't mix and match all the different poseidons necessarily. The Jetstreams work at a higher ISP than the Cyklons, Tritons, and I think the Xstream.

If you want to put any other make of reg on an Apeks 1st stage other than the DS1, you'll probably need to either re-use the Apeks hose and replace the 2nd stage, or block the port in the Apeks 1st and use a different LP port for your reg. This can be limiting if you need to put 2 regs and 2 feeds on one 1st stage. Drysuit divers, for example.

As for the jetstream US combination, the only thing like it is a guy I heard about who claimed the best combo was an old Delta 2nd on a jetstream 1st. No idea why. You're either trying to save money or you know enough about it to choose it that way. If you're trying to save cash, don't use the US as your buddies, use it as yours. That way, if it goes breasts skyward, your panicking buddy will get a reg that will probably perform much better. Unless you're on a hog rig.

Porg, your Vypers should work with most major 2nd stages. Don't go buying jetstreams though. Why not just sell them on and buy a 1st and 2nd that are up to the job? Ebay should have a few quid for side-exhaust regs?