The answer to your question depends on your typical sailing conditions and your skill level. The F133 isn't too small for someone your size if you are at least an intermediate skilled sailor (water starts and making most jibes). This assumes you have enough wind to plane when you go out on the board with an 8.5 (15+knots a rough guess).
Give us a little more information. What were you sailing before the F133? Skill level? Typical conditions? Quiver of sails and other boards?
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.