IMHO the better calibres ever are that you have chosen. Because half of the pleasure of going on safari is about to rejoice yourself with whath you are opting for. Every day training, every day checking loads, doubting no end, and so on. The "old hands" are pleased to provide you with recipes, and this way getting a lot of joy enbodying your hunt.
Keep on the good job on trying to do the best with what your are planning. Unconsciously and because you're no fool, you have taken advantage of thousands of advices from books and from forums and that lead you to no fool options.
Hunting in Africa is the first reason to buy special rifles. So be it, fulfill your dream first and don't opt for shortcuts as this is all about your pleasure first.
Asking advices? the older the hunter the minimalist his options will be, with his OWN (I insist on own) choice.
My absolute recommendation is follow your feeling and what please You most.
My egoitical peronnal option is using my seasonned Sauer 375 for almost every game, and my chapuis 470 that I never used in Africa, prefering to travel light. Stupid option but I stand to it, perhaps because I now haven't the tenth of Your commitment.
Try liberally you options. I wish You plenty of fun and also doubts and regrets so as to once again test your talents in this never ending quest for Africa hunting.
Good luck my friend and don't forget that quite a lot are living your adventure by your proxy.
Please forgive my poor English, that comes from my heart and my odd personnal believes. Good luck