Have you considered getting solid inserts from? Has-Ben's Esk8 Retirement Shop
I have gotten 4 flats in the past 3 years, thorns, glass, random metal shard and…tire liner which somehow got folded up and cut into the tube, Having adhesive is a great idea. Now I just carry two fully assembled spares with me unless I’m riding my SixShooter with the Clever 6x2 tires, those tires are tough with thicker sidewalls that can be ridden on.