Reading between the lines - a helicoil is 'supposed' to be stonger than the material its inserted into and your up-rated studs, I imagine would have fitted into the original holes, so....fingers and legs crossed you'll be ok.
SOme more info here:
http://www.roadstarmagazine.com/modu...rticle&sid=233 Some good guys I've used in the past (Cheers - Derek!)
http://www.frost.co.uk/item_Detail.asp?productID=9009 finally - a nice chopper write up
http://www.streetchopperweb.com/tech/0403stc_thread/