So I realized I never posted these pics. There were a couple of times where I built a car and then mounted sentries on top of it using SourceOP commands. Here are the pics:
This was a fun experiment.
Details:
First, I used "e_spawnprop carwhite" to make the actual car. Then attached wheels using the "e_wheel 2" command. Then made thrusters. I used "e_thruster a 30000" in the back for forward motion and likewise with a "b" and "c" group on the front sides of the car for turning. Now you have a controllable movable car.
Then, I froze the car so people would stop moving it. Then I built two sentries (one works fine, I was just having some extra fun). Move the sentries into position on top of the car using +grabent. Then, look at the car and give it a name (use something like "admin_keyvalue targetname car1"). Then, look at the sentry gun and type in the console "e_fire SetParent car1". The sentry is now parented to the car and will follow it wherever the car goes. If you want (and of course I chose to when I did this), you can give the sentry gun extra health by using the command "e_fire SetHealth 50000" while looking at it. I think that's everything.
I'm sorry to all those I owned on the red team. Thank you for participating in my experiment :P.