Okay, so I've been messing around with my had60 and plates for the past two hours and I've found something that works and feels really nice.
Background story:
I am a proud owner of a R1 Unikorn. It looks lovely... but I hate the way it feels. It must be a combination of the mounting and the switches I chose, but it has no life to it. It's really boring. The switches are gateron milky tops, lubed wtih 205g0. The springs are a bit light on them (can't remember, but I think they were TX 55g or 60g springs). These are paired with the black aluminum plate from TGR x Singa. Simply put, I hardly every use it because it feels "off."
Today:
I get my had60 in the mail. What a flexiboi! I have a full FR4 and half FR4 plate to try with it. Well, neither really worked out for me. It's entirely too flexible to use in the Unikorn case with a 1/2 plate. We're talking switches hit the bottom of the case with normal typing. The thing is, the Unikorn has very small clearance under the PCB. So any large flex is going to cause issues. I could probably line the case with thin fabric or plastic, but you'll still feel that bottoming out on the case. The full plate honestly took almost all of the flex out of the PCB. I really couldn't tell I had a flex cut PCB in it.
Then I remembered I had a PC plate cut about 5 years ago that I had never used. Oh man... it's perfect. 1.5mm PC is very flexy if you've never tried it. This setup is perfect for the Unikorn. If I press hard around the G and H the PCB hits the standoff there. So, I'll probably line it with paper or tape to be safe. However, this setup brings my Unikorn to life! This is what I had expected to feel from the board from day 1. Really happy that I tried this combo. POM/Delrin would probably also be a great solution here as well. I know that Ponoko has it in 1.5mm thickness b/c I had one cut for my Prophet.
I'm also thinking about using the 1/2 plate with the stock PCB. But that's a story for a later day.