Add my vote to those saying you don’t ‘have to’ do anything!
A. Stacking leaves marks unless you take care, gives a lot of loose cable and may encourage things getting hot if there is not much space. But, if it sounds good, it’s ok.
B. Using a book case, sideboard or whatever may well sound and look a bit better to you – it’s plenty good enough for many here.
C. Using a not-expensive rack may well sound a bit better than that to you, but this may well be room and system and ear-specific, and it is all too easy to judge the sound with your eyes.
D. Using a better rack – exactly the same comments apply. And IMHO the Fraim certainly fits in the ‘better rack’ category.
E. A few here have found they could even improve on a Fraim – usually with something massive or with extra isolation (rubbery feet, isolation platforms, lumps of wood etc). This is even more likely to be room/ system/ listener-dependent, and many will maintain that we are by now well into the territory in which most perceived changes are all in our heads.
Personally, I am in category E at home. However, I am building a new hi-fi for a holiday cottage, and that will sit on something non-dedicated and made from exciting local wood for the simple reason that we live in rooms – we don’t just assess hi-fi in them. I don’t expect to spend any time wondering after it’s installed whether a Fraim would be better.
As for ‘data to prove all this’, good luck! There are entire threads here and on PFM discussing isolation and more generally how to measure what in any useful way, who should be doing what research, whether how it sounds to the listener is a useful measure of anything (yes really) and to what extent the whole thing is ‘in the mind’ of the listener only.
Finally, I should say that I have done some experimenting with Naim cups and balls. Using them with non-Naim glass on a non-Naim rack was actively nasty to listen to. However, I am confident that they work on a Fraim. My guess is that Naim did quite a bit of R&D to make the unit as a whole work well.