I did a few diagrams for someone who wanted options for a Tele with a humbucker neck and single coil bridge, that included some with Grigsby 2 and 4 pole lever switches. They'd apply to your case as well, just with the single coil (P90) as the neck and hummy in the bridge, so it may give you some ideas.
Also, when you plug the 'front' of your control cavity you may want to include a section of maple or some other hardwood where you're going to cut the lever switch slot. That way it can be thinner and still provide more support than soft basswood. Actually, with the ply top on the TB-1TB it may not need it, but check the thickness with the lever switch shaft/lever for clearance.
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