Help! I've got a Hansgrohe Thermobalance III valve already plumbed in, but the walls are still open. I've just switched contractors (long story) - and apparently contractor #1 did some of the plumbing wrong so it'll need to be redone anyway.

One of the changes I've just discovered I'll have to make is to use a deck-mounted rather than wall-mounted tub filler (because the tub has to be turned around, and a wall-mounted tub filler would hit me right between the shoulders!). Since deck-mounted tub fillers generally come with separate control knobs anyway, I'm having second thoughts about the Thermobalance III. The rough-in valve is my only sunk cost (my trims are returnable) - if I'm going to switch courses I may as well do it now.

My question: does the tub-filling part of the Thermobalance III do a fast enough job of filling the tub? The specs say 6-7 gpm (as opposed to, say, the Kohler Mastershower valve, which says 10 gpm, and the stand-alone tub filler, which is 12 gpm). It's a spa tub, and I don't want filling to take so long that the water gets cold. (I do like the idea of filling it with a thermostatic valve rather than guessing at the water temperature).

Does the water pressure in my building (it's a co-op apartment) matter for this question? Contractor #1 was muttering about how I couldn't really run two things at once on the Thermobalance III (but I couldn't tell if that was because he misunderstood the valve - he plumbed it wrong - or because of pressure).