Joined: Dec 2004
Posts: 12,560
Likes: 799
From: Middle of da Mitten
Bikes: Trek 7500, RANS V-Rex, Optima Baron, Velokraft NoCom, M-5 Carbon Highracer, Bacchetta Quattro, Catrike Speed
I'm going to take a wild guess that your MHR is higher than you think it is. Zone 5 is not something you an sustain for long, or without significant cost.