My 91 TStar also had the wood and fibreglass combination similar to yours. When I redid the carpet I strengthened the middle floor section between the driver and observer seats. I just cut a piece of fibreglass cloth to fit, soaked it in resin and spread it over the backside of the section. Seemed to work OK.
2005 X2, Viper Red, MCX, OJ TZ-X5 prop, PPass, rear 750 sacs, KBS, IBS, Bennett Wake Plate, custom wake shaper
(previous) 2001 X5, 1991 TriStar 190