I had the same problem with the el530, they are front heavy. I found if you made it REALLY tight it would hold but I had a lot of trouble getting it off. I had to squeeze in the screw ring and pop it off. Solution was to use inner tubes.

I have two el530s mounted on the fork braze ons for training at night. Just find a broomstick or tube the right diameter and drill a hole on it for a mounting bolt. I run these with a nighthawk emitter on the handlebars or helmet. Works ok but I miss my 7 degree 12w halogen (but not its big battery and 2hr run time!). Its a nice tidy setup and I think they work better being close to the road.

I put one EL530 bracket onto my commuter and I'm waiting on two more flex-tight brackets for my mountain bike. I wouldnt swap brackets between bikes.