To be honest, shooting a training rifle will not improve your ability to shoot with your main rifle. You can familiarzie yourself with the controls and manipulation if its the same design. BUT using a training rifle WILL improve your fundamentals, which you'll be able to apply to your main rifle. If you use the same scope, or even the same style (MIL scope on Trainer and Main Rifle for example) it will improve your ability to use that scope system. But the ballistics will be different, which means your bullet drop is going to be different, and your wind drift will be different.
So with that said, I PERSONALLY would keep the scope as low as possible, or whatever is the most comfortable. And once again since you're using different scopes, you'll probably have to change your cheek weld to get proper eye relief. Another reason why using the same scope would be beneficial.
If you got a high quality mount for your scope, you could take it off your main rifle, put it on your trainer, and swap back and forth with no shift in zero. You'll than likely have to change your elevation to obtain a proper zero since you switched calibers and rifles, but if you have a quality scope you can easily switch your zero back for your other rifle by counting the amount of clicks or MILs or MOA. They do make those kind of mounts out there, so dont listen to people who say it isn't possible. I'm personally looking at a QD Lever style mount made by Bobros, but a cheaper and just as good system would be a scope mount in which you torque down two socket style bolts on the side of the mount.
I plan on getting at least some kind of QD mount, be it levers or TQ'd bolts, so I can buy a single, quality scope and then use it on all my rifles. I'm pretty good at multi-tasking, but I will never shoot two rifles at once, so why do I need a scope for every single rifle I own? If you own 3 or 4 rifles, by the time you buy a decent scope for each one, you could have easily afforded the BEST scope in the industry.
We live in the day and age where you no longer have to put a scope on a rifle and then never take it off again to maintain a zero. With quality mounts and scopes, as long as you reinstall the scope with the same torque and rail position, it will return to zero. (When installing a scope mount on a rail, its important to maintain forward pressure when torquing down the bolts or closing the QD levers to prevent the scope from sliding forward from recoil)
