They don't have any TFE up but otherwise...
I daresay qvault PAT is the perfect level of difficulty in between CDP and achiever, especially for keyholes because that's where CDP lacks.
One downfall with CDP keyholes is that it doesn't focus on proportions.
On the other hand, Achiever just hands you 10 minute brain teasers, expecting you to do them in under a minute.
Qvault...though there are some dubious answers...seems to focus more on proportions without adding in all the extra time-wasting gunk that achiever is full of. I think everyone who is struggling with PAT needs to try this, it's free (at the very least for those of us who paid for other qvault sections) and I think it complements CDP perfectly in terms of what CDP lacks.
If I ever get a score worthy of a breakdown post....Qvault is going to get a lot of free advertising from me....