The very guy you have on avatar uses pips because, coach told him he won't be able to develop long stroke. (i do not remember the source)
Anyhow, here is an hour long rant about this:
Ave,
looking for info which training ball to test (I will probably buy 3-4 packs of different ball and then buy like 140 balls). Writing mostly because I recently played with some random old gewo training balls and they were misserable.
I might sound like a broken record but with such big budget I would buy a selection of decent blades, test for two weeks (set yourself a hard deadline, otherwise you are going to be EJing for long time). Pick the one you just like.
TL;DR time to develop a any serve, including RP, depends on your current general serving skill. Also it heavily depends on what you consider "developped"...
Nobody will tell ya how long it takes. Everyone has a different baseline. I think 90% of the things you have to learn for this serve to be effective apply to every serve. Maybe the last 10% is for this serve only.
Brushing contact (applies to all spinny serves)
Service depth (applies to all...
I don't think the exact number matters. I would say only comparatively between rubbers it matters. For me this is indication:
Ok this rubber might be suitable for me, its soft enough
Oh hell no, in my current condition I will never hit through a 60 degree brick
Recently both of my Asics pairs got messed up insoles. Replacing them with gel added weight but also added cushioning. Maybe that is something you want to explore if that is important to you.
I have both Rockets and Blades. First I bought Rockets. They are ok. Then based on my friends recommendation I bought blades. Less cushion, better grip.