Thanks a lot, Eric. Now I'll have to buy yet another Cooke III Mahler 10! Seriously though, . . .
If you're going to strike the bass drum that loud and that 'sharp' like, then I think it should be done offstage. But here's what I would do:
I think it's stupid that there are two bass drum strokes linking the final two movements. If Mahler had finished the symphony AND decided to keep both strokes, I'm certain he would have differentiated them. I would have the first stroke (the last note of the fourth movement) played really loud, but offstage. Then I would do the second stroke (first note of the fifth movment) played onstage, but softer and more 'muted' in quality. I would do most, if not all of the strokes in finale's introduction that way. Then when the bass drum returns AFTER the flute solo and the big build-up passage that's dominated by the strings, I would have that first stroke be both loud, and played onstage. I would then revert back to an alternating combination of offstage and onstage bass drum strokes, altered to make the volume come out roughly the same, which either way.