A 1mm cut in the carcass ought not to compromise the tyre greatly; I'd probably run with that on the rear (perhaps with something to help stop nibbling and a heavier tube) for local runs, commuting, training etc.
FWIW I am in the midst of some 'experiments' with tyre boots. I've used all kinds of things as tyre boots in the past but many that are strong enough to resist 'nibbling' (or other failure in or near the damaged area) can chafe the tube at the edges of the boot inside the tyre, or don't flex in quite the right way with the rest of the tyre.
So my dream has always been to find a fabric that is thin enough that it won't cause the tyre to flex weirdly or chafe the tube at the edges of the boot, but that is strong enough that it will work without nibbling damage and that can be stuck well enough that it 'becomes part of the tyre' and will move with it. [Repositioning loose boots inside tyres when you puncture is a PITA; if the boot is part of the tyre one shouldn't have to do that.]
The current experiments involve using spray-on adhesive to secure several layers of thin but strong fabric (e.g. cut from umbrellas) inside the tyre. If the boot is large enough then the load can be transferred from the carcass to the boot in shear, well away from the damaged part of the tyre.
The method (such as it is at present) is to 'bias cut' cut the booting fabric so that the warp and weft match closely to the bias angle of the original tyre carcass.
A smallish patch first covers the hole (the idea being that any nibbling damage ought to be confined to this layer, at least to start with), and then a second, much larger patch (about twice the size, or up to ~ 4") to cover the affected area and to take the load out of the damaged part of carcass. The edge of the boot can be run right round the tyre bead, which ought to help it stay put should the adhesive fail.
A generous layer of talc ought to stop the adhesive from bonding to the tube.
Results so far are encouraging; after trying it on a few small cuts etc it seems to work OK; you can
just see that there is a boot in the tyre (the carcass is slightly narrower where the boot is fitted) but there isn't any sensation that there is a major difference in the way the tyre flexes; on a perfectly smooth surface you can't feel the boot (which you certainly can with thicker booting materials).
I decided to try something a bit more ambitious recently; I have a folding Kojak with a pencil-sized hole in the sidewall that I am running on the rear of an old MTB that is being used for local runs. This is a seriously damaged tyre (the boot is effectively the entire sidewall in the damaged area...
) and the stress in the carcass is significant; ~45mm wide with ~60psi in it is similar stress to ~120psi in a 23mm tyre. Yet the booted tyre is not badly deformed and runs nicely. I've only done a few tens of miles on it so far, but I'm optimistic it is going to work OK. Only time will tell if it is really durable or not, but things are looking good so far.
cheers
