So to get this straight,
You merge the left TT and the right TT tank fuel lines into one hose then run that hose into the stock tank's vent hole located at the back right corner of the the stock tank?
Then you run the TT tank vent line(underneath the TT tank) up and around the instruement cluster and attach it to the right side, kinda high up to minimize water/dust contaminating your fuel. thus allowing both TT tank and the stock tank to equalize the pressure in both tanks.
So there is NO drilling the stock tank.
Petcock stays open ALL the time.
Both tanks vent using a shared vent hose coming out of the TT tank.
In theory, it sounds like it would work! And you stated you've done this using a jerry can for many miles.
As long as you have an airtight tank, the fuel pump should provide the fuel suction to draw all the fuel to the engine.
Sounds like you have to have the "canisterectomy" done too (US bikes only).
In about a month, I'm gonna try this and will report back with pics!