Steve,
Here you go. I had a similar issue with my seats, not corvette. Until proven otherwise I believe that the Pre L cars had a sheet metal cover that was wrapped in vinyl. The L cars like yours and mine had a plastic cover that had a protrusion towards the seat. See picture below. What I ended up doing was making a plug out of wood and then making my own fiberglass version without the hump, then trimmed to fit. There are sheet metal tabs that can be bent down, no cutting required that allows for a little more room. This gains about an inch as I recall. I had to eliminate the metal ring that hold the boot down but have never missed it.
Steve
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