I was using a CRP-1 for years.
Then I was going to upgrade myself to an electronic version but ATPL exams got in the way so had to "upgrade" to a CRP-5 version.
Didn't realise how much can be done with the CRP-5, but I wouldn't be without my calculator for some of the calculations (such as density altitude calculations etc).
Wouldn't be without my trusty CRP-5 at the moment...
... unless the CAA decide to give into the requirement and allow electronic versions instead. If they do that after my last exam, well I'm not going to be a happy bunny!
Best wishes,
Charlie Zulu.