I have just ploughed through the massive tome from the UK Motor Sport Association of competition vehicle build rules and all butt welded suspension mountings should be braced or gusseted. The M3W in theory therefore, could not be used as is for motorsport if you had a fussy/knowledgeable scrutineer.
Wilson
Ouch! Although it is notable that MCC do not (AFAIK) have a competition M3W5sp. Meanwhile I am wondering if the fuel tank mount crack issue is another recall-worthy roadworthiness concern for MCC to consider. But I may be biased as I'm a victim of that fault!
A reasonable question PaulV
A Morgan Identified Fastidious Owner... 2011 4/4 Bespoke, 1981 Delorean, Auburn Boat Tail