Hi Andrew —
Happy New Year!
To be honest, I don’t have very strong opinions about adding a fifth section (I believe other prep resources may perhaps encourage it more strongly than I do) —
I do think it’s good for everyone to take at least a few pt’s with 5 sections, and I think it can be especially useful as you are getting closer and closer to test day, but it’s up to you as to whether you want to implement it for every pt (and I’d just base it on whether you find it helpful for increasing endurance/etc. or not) —
In terms of the experimental sections themselves, I think the best sections to use would be ones where you’ve already tried the problems as part of your drill work (so that you don’t end up wasting fresh material) — but I could also see the benefit of trying an extra fresh section if you wanted to do that as well (you could purchase an additional, older book of 10 for experimentals + extra drill practice) —
HTH — Good luck with your studies, and if have any follow up just let me know — Mike