TMax 400, along with TMax 100, sees rather far into red; so these have good linear response not only to 25 medium red filters, but also 29 deep red. Not all films do so well with deep red. I've noticed my B&W 29 is actually a little deeper and than my Tiffen 29.
But the best thing that could happen to Bill's, "Add this and that together, then maybe subtract that, then examine the entrails of an owl and the flight path of pelicans" ... would be to ignore all of that. Just go straight to the sum filter factor itself applied to a direct scene meter reading, and don't meter through the filter at all. So much simpler and more reliable!
With most pan films, the filter factor for a typical 25 red filter is 3 stops. LIkewise for a 29 red in the case of TMax films. But for other films, you might need 3-1/2 or 4 stops for a 29, or might more wisely avoid deep red entirely.
Bill, there are all kinds of granite, some of it dark absorbing heat, much of it light, reflecting heat. There are also big differences between deeply weathered and pitted rock and smooth glacially polish granite, which can be almost reflective. I grew up amidst granite and granodiorite, and have taken innumerable shots of it. I wouldn't worry much about IR. But if someone wants to play with the idea, they can simply buy some near-inrfared film (I don't know what is presently available - I once used Konica), along with a 29 deep red filter. More often, it's going to be foliage which is the big surprise.