Firstly, from many other threads, it seems that most people vomit whether or not you take AEs. So taking multiple AEs would be a needless complication, risk interactions and side effects and possibly increase the chance of vomiting. In fact, I'm sure I've only read of one instance where the person didn't vomit. I think we can all count on vomiting, regardless of AE - what matters is how quickly that happens.
My understanding of it from others is that motion sickness med (the antihistamine) will not help.
And the purpose of using a dopamine blocker is to delay the vomit to allow the critical amount to be absorbed first. Also, there seems to be an added effect from meto of speeding absorption which is what's wanted- I think?
Also, from reading the protocols and several further threads here, taking too much SN is counter productive and again risks vomiting too soon.
For what it's worth, I feel that the right thing to do is stick to the 25g with a simple protocol of one antiemetic and not add unnecessary complications like extra SN or extra AE.