The tank is pretty much up against the bottom of the wheel well. There was room for an 8mm filler pipe to come out of the bottom of Marie's wheel well and head back to the filler, but only just.
Having said that, removing the wheel well itself would liberate a little room and, as said, I would go for a centre filled toroidal with the valve located to the front, which will bring it out just behind the diff where there is no problem routing pipes. Spacing down the petrol tank is also an option, although if you have a shinbreaker I guess you'll end up with clearance issues before it's dropped too far. Other option is to ditch the main petrol tank and use a small one?
One consolation is that the petrol tank should mean LPG tank to ground clearance is a non-issue.
As far as I can see from the documentation, the stag 300+ is pin compatible with the 300 so probably backward compatible. I think the premium has a couple of extra wires for the OBDII link. Might be possible to add these in-situ but, TBH, I'm inclined to think self-mapping is no big deal. It's the flexibility to manually map it for all load conditions that I'd like to see. The petrol ECU is already doing the self-mapping bit. No advantage in 2 ECUs doing it, other than quicker install IMHO.
Kevin
Car will have a shin breaker, both for the LPG filler (as I don't want to make a hole anywhere in this one) and for the obvious
Holiday Home but I believe it can be done without a bar along the tank.
Could drop the tank a little and intend fitting a top mount, full toroidal with the valves at the rear of the car (as I reckon that orientation will make most sense) although you may have a valid point putting it the other way around for ease of routing the 8mm pipe :-/
Smaller tanks could get a bit complicated IMO, although bears thinking about if you have any ideas :-?
Teilo doesn't think there'll be a massive benefit fitting the newer
Plus ECU to an Omega... And the self learn is on his own ECU, not the new Stag one. He's done it because he found a lot of the (admittedly foreign) installers he visited had no access to a laptop with a working battery and were just running the auto calibration and letting it go

This way they can stick it "learn" mode and check it at the 1000 mile service

It also negates the need of having someone sat there who knows what they're doing (to make life easier) when you calibrate it
