Dubbing/cloning to multiple VTRS

I'm sure this must have been asked answered in the past on the forums, but a search yielded no results.
I was once told that under no circumstances should I ever dub to more than one (HD)SDI recorder at once. I was not given any reasoning, but the person who told me came from a big dupe-house so I took his word as gospel.

Since I was told this, our deck collection has grown, and (provided there is an option) it has become highly inefficient to dub to one tape at a time.
If I need to make a few HDCAMs and a few Digibetas from a HDCAM master, I will dub them one by one.
Our setup is 1 HDCAM recorder (D1800), 1 HDCAM player (JH3), 2 Digibeta recorders (A500P).
Can we have the JH3 playing and the other decks recording? If so, would the setup be-

Video and Audio: JH3 ---HDSDI---> D1800 ---SDSDI down convert---> A500P(1) --- SDSDI ---> A500P(2)
Timecode: JH3 ---HDSDI embedded TC---> D1800 ---TC Out--->A500P(1) ---TC Out ---> A500P(2)

Thanks in advance, any help will be hugely appreciated :)