OK, the pressurized tank proof-of-concept solution. One two-way valve. Position 1 vents as normal. Position 2 closes vent path, opens path to pressurizer bulb (from a blood pressure cuff). The bulb provides more than enough pressure (inches of water, no problem of stressing the tank) that pushes fuel from TAT to main tank. It works really, really well.
Now for the next to final install.. I want to buy a valve with npt threads in order to reduce valve height. I found a shorter nipples, shown below. As is, it clears the Givi back rest, but want a cleaner look. Additionally, after I get a Lynda or other cover, the bulb will be inside a pocket.
Oh, the overall reason for pressurizing the tank is to A) quickly displace fuel from TAT to main, B) more importantly, when both main and TAT are close to reserve levels, I want to move all TAT fuel up front. That way I KNOW exactly how many miles I have left. Otherwise, knowing me, I'd think 'WTFO, I *should* have some left in the TAT, it will be OK." But since I've not found a low pressure pop-off check valve, if running uphill, you can actually drain the main back to the TAT. This way, fuel levels are a known constant, not a variable. And for a CandyButt Association Rider like me, that's very important you know.
Relocated the bulb so I can access it when riding..
Added a back rest - here's the views. The back rest needs be cut down by at least 50% to provide seat room, but the concept works. Currently, I'm using Velcro. After determining the correct thickness, I'll fab and weld an adjustable rail to the tank so I can raise and lower it, and hopefully even have the pad articulate vertical position.
BTW - I hit a MAJOR pot hole last Saturday while on a goat trail - lost focus, was watching a huge RedTail hawk with dinner in the claws.. Nailed that pothole square, rear tire off the ground, magnetic tank bag flying loose, feet off the pegs kind of ride - and TAT did just fine. Thankfully, so did the front rim.
