I am pretty sure the outer ring in aluminium and over tightening will strip the threads . I put a little loctite on the threads and make sure the first nut it tight and just tighten the second one up just enough to keep it in place
Lol , no it wasn't the same guy . The chap I was talking to does know his stuff but has since moved to another store and do not have much confidence in the other staff so no longer use my local ..
I was talking to a guy that works in Halfords a month or 2 back and he said motor wattage was going to be going up though I took it with a pinch of salt ..
Though I have seen some big brand bike manufacturers with 500w motors on uk sites