Driving schools usually let cabs in so long as you wear a helmet and the roof is up.
Being a former cab owner, the M3 Cab felt like a bloated pig on the track, lots of understeer. Just wasn't fun.
Since you are a Canuck....both Cayuga and Shannonville will eat your tires like crazy. Mosport is bit dangerous if you haven't tracked before.
The M3 cab will like have a 350-400 pound weight penalty.
"Aerodynamics are for people who cannot build engines"......Enzo Ferrari