OK, some progress
VT and some others might be interested on this concept of fuel line unions to fuel tank:
* Use on truck/tractor tubeless tire valve assembly
See first picture, standard item has pretty much correct stem to popular 1/4" tubing, the thread part on the tip is about 7,6 mm, a tad small for standard 8 mm tubing.
Good news is that they are readily available, pretty cheap (I walkked in first tire shop and they sold two 3€ apiece) and when the air valve is taken out it is all smooth bore. They had straigh stems, 90 degree, short ones, long ones, but I liked this small angle model.
The interesting thing is that I just might be able to have the cake and eat it too, very soft fuel line might allow me to fit original tank and a quick fuel disconnect. Threre is only about 50 mm of linear distance of two fuel lines to snuggle. Rubber hose would not make that tight bend, but this Oregon fuel line just might. Only thing is that I need a bigger one than this 1/4" I have.
See pictures two/three.
Another complication is that I can't fit very well the filter assembly I have, it is just few centimetres too tall to maintain and use it properly. Darn. I don't want to tilt it, nor mount it to protrude out of the pipe frame at all and thre should be enough space around it when maintained in dark, rain, blizard or -30C and windy.
On the other hand I want it as big as possible in filter area, because this has no transfer pump.
I'll try to fit the original tank and injection pump with new diverted fuel lines and see if it looks doable, if it does, then I'll hook them up to an external filter that has aux fuel line disconnect. That would give me max. flexibility and if I get the filter height right, there should be no problem when bleeding it.
It all would be a whole lot easier if I had fuel rubber line T with short end of 50 mm stump, I have seen them on car cooling systems, but never on fuel lines.
Plan B is to take the original tank out and make a good use of the space where that orginal tank is. For this option an fixed tank would be great. I googled last night ready made tanks and there seems to be many possible ones in USA, but not that many in Europe.
Pekka