For Pebble Tec start-up, your best bet is to ask Pebble-Tec (the company, not your dealer). They are the ones who know what's actually in Pebble Tec, and how it might react: http://www.pebbletec.com/service_support.aspx

However, their pool chemistry instructions are pretty much industry boiler-plate, which means they (a) really don't know or (b) just want to CYA by saying the "OFFICIAL" 'right stuff'. If I were you, I'd call (and then recall) till you happen to luck onto a support phone tech who actually knows something besides what's in their phone script.

BTW, the Jacks Magic product line is not bad, but it is seriously over-hyped and involves some deceptive elements. For example, the "Blue Stuff", "Pink Stuff", "Purple Stuff", "Step Stuff" and "Blue Vinyl Stuff" are all the EXACTLY same thing (HEDP) except for the dyes.