Coupled Wheel Back to Back for 12mm Track?

[natterjack]

Appreciating  the project in hand is not strictly 3mm Scale, I hope the practical experience of this forum can answer my question.

 

My Hornby TT120 coupled drive wheels have a b-to-b of 10mm, my Gaugemaster b-to-b 12mm gauge is 10.2mm (ish) and the 3mm Society standards suggest up to 10.7mm (0.4mm flanges). Now the Hornby spacing seems to work fine on current commercial track and I can see certain advantages for the slimmer option for rigid chassis around curves etc. In addition, the Hornby locos have @ 0.5mm side-play on all the drivers.

 

What b-to-b ought I adopt for a scratch build 4-6-0  using 14mm N Gauge tyres with 0.45mm thick flanges for the drive wheels? Track and point-work will be a mix of Hornby, Tillig and Peco TT120 12mm.

 

The pertinence of my question is that the wheels will be bespoke 3D printed together with a quartering assembly jig that  includes the appropriate b-to-b spacing  in its design.

 

Thanks in anticipation.