The standards are to suite the gauge, in principle. It's surprisingly difficult to find the standards on line, but you shuld be able to use the dimensions of any 3 1/2" gauge loco.
These are what i settled on for Southam, which is an 0-4-0 which is pretty much the same size as Tich, and it has run OK on at least five different tracks, including Derby which has points! You can even use Tich castings for its wheels, so these dimensions should be fine.
Neil
