I'd be interested to know which cheap, reliable backups you're getting. I was thinking of getting a passel of Picos as backups, but I'm open-minded (and suggestible and somewhat fickle).
Was interested to discover that the new Zenith tank I filled yesterday behaved horrible on the JAC Vapour but does well on the SX Mini. I don't understand why--the tank/coil must be okay since they're performing well on the Mini, and the tank that was on the Mini is now happy on the JAC, so the mod is okay (thank heaven, since it's less than a month old). Just a Christmas fluke, I suppose.
How was it misbehaving?
As for backups
Here's some pocket friendly options:
Pico 25 80watts - if you see them cheap somewhere. This model will fit attys up to and including 25mm
Wismec sinuous p80 - good around mod, almost tube like in shape. No limit in atty size unless you don't like overhang.