[embee]

If the clip-on is clamped predominantly on the extended top cap (35 out of the 40mm for example), there will be precious little to stop the clip-on unscrewing the cap. The std clip-on has a security bolt through a tab into the underside of the top yoke which prevents rotation round the stanchion. If you could configure something similar it might be feasible, but be cautious.

I fitted modified FJ1200 clip-ons to my curvy S. You need to grind away some metal (steel forgings) from the riser part to go past the yoke boss, and I fitted them reversed left/right to get the right position. This raises the bar significantly while leaving them clamped on the stanchion under the yoke. I also welded on a security tab to replicate the original, and of course it needs a threaded pad on the right for the brake reservoir. Not a simple conversion but do-able if you have the facilities.
Alternative bolt-on bar conversions would be a lot simpler even if pricey.