I cut and glued in the cockpit floor. Before gluing it in, I added blocks under it where the rudder pedals will mount. I also cut and glued in the plywood bulkheads for the horizontal stabilizer and the longeron doublers right behind them.
Urethane foam for soundproofing
floor installed and already messy
1/4" birch at firewall with light pencil marks to show where blocks are underneath