In general, using high-speed range mini motors (> 2.2 Kg.) in big wheels (<24") is not a good idea.
Without going into a lot of detail, the problem is they can't get up into the RPM range where they are most efficient. This is called a "Current limited system", whereas a mid or low-speed motor will rev till it just won't rev anymore (RPM limited system).
The way this plays out in the real World is that a mid-speed mini (260) powered by a 20 Amp controller on 48 Volts in a big whl. will top out in the 23 to 25 mph range and a high-speed mini in the same system will not go any faster, it runs out of Current. The bad effect is, the controller tries to supply max Amps most of the time (especially on hills) and this tends to melt things like the Phase wires and connectors and, in the worst scenaro, the windings in the motor.
Installing them (I'm assuming you are building a 2WD) in smaller wheels would certainly help, but if you can't, it still might work out. Your "saving Grace" is the 2WD set-up. As the motors work together, they tend "pull" each other up into a higher rpm range.
I rode a 2WD for a year and it consisted of two Q100's (2 Kg. ea.) high-speed (328) motors on 48 Volts in 24" whl.s. They mounted big tires so their overall height was like a 25" whl. w/ a 2.0" tire.
On a single motor (either one), top speed was around 23 mph, but together, it was a blazing fast, 27 to 28 MPH! It would take off well enough, but in the mid range (15 to 20 mph), it was really slow.
I now run two mid-speed motors (260's) and while I only gain a 1 or 2 mph using both, the bike pulls smooth and steady thru the entire rpm range. Where this set-up really shines is climbing hills and there is not much I encounter that I can't climb. The high-speed motored 2WD was so-so on hills at best.
If you think are going to be trying to climb steepish or long hills, I would rethink the high-speed motor/big whl. idea.