What I would do is make stepped coupons with each step wide enough to take HRC readings something a little less thatn 1/8" thick and then step up a couple of times to your .20" . What I actually do is make a wedge shaped (flat ground blade cross section) that is around .062" widening to .312" at the top and around 1.5" wide and then cross section it to Rockwell the end and determine depth of hardness. If going with the steps I would narrow your piece to 1.25"
The chrome should actually increase the depth of hardening a bit but it is still only 1084 and the chromium is not that extreme. P#50 should do the trick and is about as fast as I personally would ever go (water is for drinking in my shop and never for quenching).
That's great, I like the stepped coupon idea. I think that maybe this should be a first step whenever I attempt a new to me steel, so much more knowledge in a condensed format. I'll try to make up a couple of stepped coupons this weekend, I'll have to mill the steps but that shouldn't be an issue. So if correctly understand your 'wedge' you actually end up testing Rockwell on what would be the internal (depth) section of the blade? Brilliant, I'll need to get some thicker steel to try the wedge.
BTW where did you get those gloves you used in your ABS heat treating video? Also it's a great video. very helpful.
Thanks Kevin!