The old W-W handout loading pamphlets for their powders showed 24.0 grain of WW-296 with jacketed 240 grainers, and 25.0 grains for castings of that weight. I have always been pretty conservative with WW-296/H-110, and followed The Book very closely with that weird stuff. IIRC, the late Ken Maugle (rangemaster at Inland) originally mentioned that "House Load" you speak of, and I confirmed it with the pamphlet and some then-current loading manuals. All sources hewed pretty close to the published data, so "When in Rome, do as the Romans do."
ETA--Most of my S&W 29-series revolvers have had 4" barrels. Unlike the longer tubes, the 4" guns recoil straight back into the hand rather than rolling up, so the 240 grain fast-steppers smack your hand a bit. The 24.0 x 296 loads usually clocked in the 1250-1275 FPS range from the 4" tubes, and ~1325 in the 7.5" barrels. St. Elmer was right--with his 240 grain #429421, 1200 FPS is all you need. I would add that in a 4" Model 29, it's about all you'll want as well. That bullet at 1000 FPS is well-nigh PERFECT in the 29 x 4".