so far it appears ok - see pic. when on stand (as in the pic) its stretched to about 160mm, so i guess is a little longer temporarily when putting the bike on the stand. it only went on today so only a few test trials to comment on - it isn't deformed yet and it holds the stand much firmer to the frame when up than the proper a10 spring did. again, this is a swing arm a10 (sorry if this is becoming a thread hijack)
i asked the wrecker for a honda 500/4 spring and he gave me a box of random springs to rummage through. so no idea what its from. time will tell if it lasts the distance.
and the spring stretcher above made it easy to fit