Best value for the buck, the staton kits are bomb proof you will be amazed by the quality and ease of operation, living in a dry climate los angeles friction should not be a problem, as wet roads on the other hand could lead to slippage. The rollers they are flat, concave would be a nightmare messing around with tire pressure. Contact surface is not a problem, you just lock the wheel down at whatever pressure you are comfortable with, this is someting you will get used do doing over time.
I have just fitted up a slightly used staton kit fitted out with the mits 43cc engine and a 1.25 roller.
I have yet to find out my speed as my speedo is useless, cruising i estimate 25 top speed 30, i weigh around 175 lbs. I might go for a slighty bigger roller, but the bigger the roller the more top speed, but the less hill climbing..bottom end torque..
engine wise 4 stroke clean and simple and quieter, 2 stroke oil mixing is required, noisey but plenty of raw power, once you hit the throttle,.... bye...
NONE of these engine are quiet unless you do some major retros to the stock exhausts, some just sound less noisey than others.