If you are committed to building a study plan around UWorld, then you should fit them in after your comprehensive review. That is where they'll be most useful. The plan above is excellent in terms of timing, but you need to pick the right materials for weeks 1-8. I'm in the minority here, but I didn't find their questions to be as helpful (realistic) as other resources and while their explanations are definitely much better than AAMC's, they are not the best ones you'll find. Maybe my situation is different than most but I don't have the greatest GPA and took it after my sophomore year. Review and learning the concepts was what I needed most. I benefited the most from starting with questions that scaled up in difficulty as you did them and that had explanations which combined conceptual material and test reasoning. Because I used great materials for the first half of my review, by the time I got to UWorld I found them easy and eventually stopped using them. I did about half of their questions and moved on to AAMC.
Pre-Week: Read the AAMC MCAT book cover to cover. Get a big picture of what you need to do.
Week 1-8: TPR for P/S adding the 300-page doc in around half way. TBR for the sciences. That is where you will find truly the best explanations. Use anything for CARS you can find.
Weeks 9 and 10: AAMC Q packs, TBR Phase 3s, UWorld questions, AAMC Section banks.
Weeks 11-14: Two FLs per week including one day to take the exam and the following to thoroughly review EVERY question.
Week 15: EK questions for rapidfire reviewing. Take your last AAMC FL.
Week 16: Go back to the AAMC MCAT book and make sure you know about every topic they list. Write out review notes for each topic.