Pannier/rack mounting - help please.

So I've converted the GFs bike to accept a rack using a seat clamp as pictured below - racks a Tubus Disco - however suffering from serious seat post slippage as the pinch points split is opposite to the seat tube's split. Have tried carbon friction paste and no luck.

My only options as far as I can see is:
Restore original seat clamp. Procure excess seat tube as shim from somewhere and run it attached direct to seat post?
That, or does anybody know of a clamp without a lip at the top allowing it to run slightly lower and below this rack clamp that does have a lip stopping it from being run lower?? Option 3 is reverse of above and somehow removing he lip of the the £7 seat clamp and running that as the lower one - I'm concious that running it at the top might be too high for the rack mounting system.

Help?

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Anybody?

P-clips won't work due to the tube profile...

10 minutes with a half decent file will have the lip off any seatclamp.

There are seatclamps available with rack mount and slot at the same side.

I did exactly the same mount with a disco on my son's tiny Isla 26er. I used the normal clamp that came with the bike, just replaced the bolt so it could accept the rack stays, plus some washers and a nylock on the end. The bolt normally binds onto the clamp in a threaded hole, so I just made sure it was very well torqued on the bolt-head side before tightening the nylock on the other side. Seems to be holding up fine.

Come to think of it, have you tried simply applying washers everywhere? They make grip and some give where bolts and machined parts aren't holding well.

Thanks chaps, managed to make a shim out of an old carbon steerer spacer slotted that over the post - put the original seat clamp back on and mounted the other clamp just over the shim.
The racks not load bearing so it'll be alright as is. So if you see anyone out on a Bianchi with many pink bits and a poorly fitted rack I take full credit!

I don't get it. If the racks not load bearing then what's it for?

The racks not load bearing so it'll be alright as is. So if you see anyone out on a Bianchi with many pink bits and a poorly fitted rack I take full credit!

It's only going to have a small dry bag with a t-shirt and trousers in. The force of any weight will be on the QR axle rather than the somewhat bodged clamp which is there for stability. Perhaps I should have said 'clamp' instead of 'rack'..