Water/IPA - Flaws in my thinking?

Planning to brew an IPA this week.  Been trying to dial in my water procedures for an IPA.  Here is my basic goal:

100% RO Water
Ca = 100-125
Sulfate = 250-300
Chloride = 25-50
Bicarb = <40
pH = 5.4

Problem I am trying to solve - I want to achieve mash pH of 5.4 without getting my Bicarbonate # too high, and without adding lime or chalk or anything like that.  But, I also want to achieve the higher sulfate #'s that help an IPA.

Using B’run Water, 5 gallon mash water, I will have 6 gallons of sparge water treated.  Collecting 8 gallons into my boil kettle.  Plan is to treat mash and sparge water the same as far as initial salt additions.

Basically, if I use:
gypsum = 1gr/gallon
epsom = .2 gr/gallon
CaCl = .2 gr/gallon

I get:
Ca = 77
Mg = 5.2
Na = 8
Sulfate = 170
Chloride= 29
Bicarb = 16
pH = 5.38

These additions get me the pH I am looking for roughly (5.38).  I was then just going to add the more mineral additions to the boil kettle. 
Boil Kettle addition:
Gypsum = .6gr/gallon (4.8 grams for 8 gallons)
Epsom = .2 gr/gallon (1.6 grams for 8 gallons)

If my thinking (fiddling with B’run water profile) is correct, this should get me to boil kettle of:
Ca = 113
Mg = 10
Na = 8
Sulfate = 278
Chloride = 29
Bicarb = 16

Thoughts?  Are there any major flaws in what I am thinking about doing?  Am I missing something?  Is there a better way to go about doing this?  Thanks for any thoughts.

Yes, you can do it that way.

Sierra Nevada adds a dose of kettle salts to the boil.

+2.  Been there, done that.

I add the excess to the sparge water… But expect most of it makes it right Into the boil kettle.

FWIW…you can mash everything at 5.3PH and adjust up or down in the kettle.

Hmmmmm… That makes sense, and I guess I was not thinking of it from that angle.  But, why then, do people recommend targeting “5.4” for an IPA (or 5.3 or 5.6 for some other beer)?  I never really see much about targeting boil pH? 
If using this method of not worrying about mash pH (within the normal range of say 5.2-5.5ish)… does that mean that the real “target pH” is a preboil pH of 5.4 for an IPA??

Yes 5.4ph in the kettle.

I feel like I have spent a lot of time thinking/worrying about “mash pH” all wrong then … Is all “mash pH” for every beer completely irrelevant  - so long as it falls within the approximate realm of 5.2-5.6?  The only thing that ever matters is the kettle pH?

For instance, a mash pH of 5.2 for a porter is just as good as a mash pH of 5.6… but, it would be good to bring the kettle pH up to that 5.6 since it is a darker beer.

and

A mash pH of 5.6 for a Helles is great, so long as you bring the boil pH down to something more like 5.2-3?

IME recently, yes. Mash temp and mash ph really come down to starch converted to sugar and fermentability of wort in the ph range we as Brewers target. I have adjusted up or down in the kettle, and achieved what is needed ( smooth dark beer at 5.5, IPA and APA with hops shinning 5.4, and crisp pils lagers at 5.1-5.2.