There are basically 3 places to attach the front strap.
1. to the fender brace, which is where I do my bike of choice, the Sun 7 speeds.
2. tap a hole into the bike frame, secure with a very small bolt and loctite the newly threaded hole.
THERE IS NO WORSE FEELING, than to be cruising down the road, and something snap or give or pull away, have that strap "come loose" and the engine slip backwards, pulling the throttle to full blast.
For insurance, add a zip tie somehow, somewhere, to be a backup for the strap.
Oh, the third way to attach the strap probably is the one where no zip tie is necessary. You ream out the hole at one end of the strap, twist it 90 degrees, and attach it to the seat post, where that bolt is a bit larger than the hole.