recording to Reel to Reel directly from "preamp out"

I tend to think yes, if there is a R&L channel output & maybe a switch. After all, I believe that is whats happening with a tape loop with the Monitor which is for convenience I believe. I've recorded a bunch of tapes but bever like this. As Oldhvymec says, be very careful and monitor it through the tape deck. If [possible I'd ask the mfg or whoever you bought it from. You are on untrod ground and there may be factors which we are not aware.

Just remember preamp out is variable output

Good call @millercarbon. That's something very important that I had overlooked.
A question though?

Then just remember if you do try and monitor using the power amp the signal coming off the tape deck is driving the power amp.

When using the Preamp out, doesn't that take the amp out of the system? IOW disable it? I would think so, unless using Y adapters. But I cannot see any advantage to that. He should be able to moniotor it with the tape deck headphone output. What am I missing? Thanks