De Havilland material & construction questions

I'm working through the videos (which are exceptional) and am gathering up supplies! I have a few questions from what I've been through so far:

1. I don't have access to a splitter so getting material will be easier if I stick with one material for the handles, zip reinforcements, handle attachments, etc. The handle video recommended thinner veg tan with glued, thin chrome tan, but I'm assuming something like 2mm veg is fine, even for the handles (using no chrome tan backer)?

2. For the main zip that's cut down from a longer length, is there a reason it's better or preferred to end up with a bottom zip stop on one end but separate/split stops on the other end? The last zip I installed using a cut-to-length zip, I used a bottom stop on both ends by running the pull all the way through and off of the zip, peeling the zip apart at the bottom just a bit, and re-inserting the pull and sliding it partway up the zipper. That leaves the zip closed on both ends with the pull installed, allowing you to crimp closed end stops on both ends. Just making sure I'm not missing an obvious reason the split stops are used. High end makers I've seen on IG have used the split stops too so I'm assuming there's a less I've yet to learn.

3. For the bag bottom veg tan reinforcement, I didn't see a callout about recommended thickness but I'm guessing something around 3mm?

Thanks!