I have seen the photo, with description, elsewhere, but can't remember where. Maybe Jeudy? Seems odd that the people at GBM haven't got chapter and verse. I'll have a look for it at this end.
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"Sometimes things that are not true are included in Wikipedia. While at first glance that may appear like a very great problem for Wikipedia, in reality is it not. In fact, it's a good thing." - Wikipedia.
 I'd guess the St-Chamond 120mm gun weighed about 2 tons compared to about 1 ton for the 75mm St-Chamond or 75mm Mle 1897. There isn't enough room in the forward part of the St-Chamond tank to mount the gun further to the rear without running into the engine.
Regards,
Charlie
-- Edited by CharlieC on Sunday 4th of May 2014 01:02:58 PM
Would make an interesting kit conversion - lots of those oddities coming out of the woodwork these days; some kits produced almost from a bit of a sketch on the back of a fag packet.
For those who aren't into engineering, a cardboard 30-fag packet was used on site to give foremen instructions on urgent modifications, including sketches, that then stayed on site as part of the documentation. Was a bit of a bugger when I gave up smoking!!