I’m Liking your approach and your style @supersecretjim, you’re doin it without a net here and you’re good humored enough to take what comes.
I’m pulling up a chair. 
Question, when you are bathing your Phat and frosty top buds with 1000 ppfd, how much of the photon flood is getting to those branches way down below?
Serious question, if you want to avoid frying those upper buds you won’t be dropping much down below.
Your manifold HST idea is worthy, but it doesn’t support high yield usually.
Another Question, Why don’t you just squeeze the HLG350 into that little tent. and try it for a bit? Physically too big?
-Grouchy
PS, those Vipar lights are still on sale…
PPS, You are running Octopots? 