Re the discussion on axle boxes, it is worth pointing out that the GW and SR had inside cylinder engines with the same (or similar) size of cylinders which restricted the length of the axle journals. I suspect the real problem, and the solution, was that the MR and LMS used 'crown' lubrication for axles and not the 'underkeep' style which Stanier introduced to the railway.
Stanier was told to change the 'crown' lubrication to 'underkeep' for the 'Royal Scots' and that class then had its problems solved, but this solution wasn't applied to the 'Austin 7' class, the more the pity. I share the view expressed earlier that minor changes to the 'Austin 7' would have improved the engine no end, but it has to be remembered that these were new engines at the time and the railway, like all businesses at the time, was under considerable financial stress and it might have been a financial issue as well as an engineering one to go back to the Accountant ask for more money at a time when the LMS was borrowing money at a discount.
There is also the issue of the politics of the new man ie Stanier. Fowler's reputation had been pretty well shredded and I doubt if anybody who valued his career would have championed one of his designs and pointed out the obvious, ie a 7F with underkeep lubrication and Stanier 8F wheels would be a winner as a mineral slogger. To do so would have undermined the case for the 8F. Not a good career move!
By way of parenthesis, it might be worth pointing out that Beames, whose upward mobility had been terminated by Stanier's arrival, applied underkeep lubrication to the various sub classes of LNWR 0-8-0 while rebuilding them to the G2a and this was a major reason for the success of the class in subsequent years.
Regards