...Whether to permanently widen the track by 0.3/0.4 mm or something else is a difficult one to answer as it immediately will cause others to say but you are not true scale if you lay straight track at 33.3/4mm. This is a circular conundrum ....
In the last year or so I have built S7 track for the following:-
* LNWR 30' rails with 10 sleepers per length;
* LNWR 60' rails with 20 to 24 sleepers per length;
* Met Rly with 30' rails and 11 sleepers per length;
* GWR 32' rails with 13 sleepers per length;
* GWR 44'6" rails with 18 sleepers per length.
And the point is?
Blow the discussion about gauge widening, which of those five different rail / sleeper arrangements is going to be offered in flexible, ready to lay, track? Noting that none of the above works as a simple mulitplier to one length of RTR track.
Whatever you offer as RTR S7 flexible track, with or without gauge widening, a fair proportion of potential customers are likely to be disappointed if prototype fidelity is an important criteria.
regards, Graham