Nige,
You could try cutting the inside portion of the wheel off, this would produce a slimmer wheel and the staggered ribs will sit in their correct profile and shape. If your tyres are glued well you can use them without inserts, the key is (as Steve said) is to make sure that the tyre is flat across its width so that the centre of the tyre is touching the track as well as the outsides of the tyre.
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