I have both those brackets already and pretty sure both will fit - the hole is towards the front of the fork. My only worry is it working loose and slipping into the front wheel. But maybe with sufficient loctite it will be fine.
Your normal fitting at the front of forks also doesn't just fall off?
Think quite a few people hve their lights mounted to the underside and are still riding.
it is a supernova adaptor might be too short in your case though...
alternatively