Sounds like you have done well on the "you" issue. I still have a bit of trouble with "you" even after all these years, esp as you say, if it comes up frequently. In contrast, "ion" has always been ok for me. I think it's that initial stretch of the ring finger up to the "y", knowing that "o" is next, that seems to disrupt my natural flow.
FYI, when I type "you", I don't stretch my ring finger up. I shift my whole hand up slightly instead, so it's almost like typing "i/e" as far as my fingers are concerned. I float my wrists, so this happens naturally for things sequences like LY and JU also.
However, I wouldn't claim that I've solved the "you" problem. I type pretty slow in the grand scheme of things, so typing "you" at 80-90 wpm pace makes it a fast word for me, but others would be complaining. If I try to do the motion significantly faster, I make errors. I think I'm mostly just much closer to my theoretical peak for "you" than I am for other words that have hand alternation or are simply less easy for my brain to see and react to.
I should also note that I've actually been practicing the "you" movement since before I choose Colemak-DH! When I was researching for the best and most practical alt-layout for a split columnar keyboard, I found something that spoke highly of Colemak-DH but noted that turns like "you" and "ion" were potential downsides. So, I opened up notepad and typed "o;i o;i o;i o;i" and "l;j l;j l;j l;j" repeatedly to see how much it bothered me. Going in knowing that those movements were trouble points was probably really helpful. I also have had no lingering issues with R and S, probably at least partially for the same reason (switching cold turkey was also a benefit here).