If memory serves... The CB radio antenna operates in what some call a "ground plane" mode. What this means is that the shape of the transmitted signal will be largely determined by the shape of the mounting surface.
The ideal location is dead center of the vehicle. Not the center of the roof as the hood surface acts as part of the plane.
If the antenna is mounted at the right rear corner, it will "throw" the signal towards the front left as that is where the majority of the plane exists. Same thing holds for any other than perfectly centered mounting location.
Is this a major issue? No, not really. Folk have been mounting glass whip antennas for decades on top of the cowl area, opposite of the car radio antenna, without major problems. Will is bias the operation? Yes, it will.
Do you have to run a 102" antenna? No. That length is actually a quarter wave antenna. Not a full wave as the wave length of the CB is roughly 36 feet...
The common glass whip is an eighth wave (54") antenna and works just fine. Antenna configuration does not become "critical" until one gets into running 2 meter radio. Then, it matters. For a CB? Not so much as long as the SWR (standing Wave Ratio) is as close to correct as possible. Some radios today have an SWR meter built into them otherwise, purchase a meter in order to tune the antenna.
Here is a link to explain:
http://www.rightchannelradios.com/tuning-cb-antenna-adjusting-swr
It is easy to get lost in the minutia of antennas.
I do have to remind you that this is all "if I remember correctly" in nature. The last time I took an ARRL (Amateur Radio Relay League) antenna course was in 1967...