You can twist an endless also, I like about a twist per inch,but when you are in R and D mode,I'd say twist all you want,then measure length for next string.
I think going from 0 to 1/4" tiller will make a very small diff,but that is speculation on my part.
If you narrow the tips,you will lose weight(?how much),but also lose reflex,I'm not sure that will help you.
Have you chronoed it,it is hard to tell speed by eye unless it is a lot(for me anyway)
The stabilizer will absorb shock,but not put more to the arrow IMO
I kinda like the riser!!