Whenever we stray from the exact bullet in some data, we have to make sure our case capacity under the bullet is as close to the same as possible, or adjust accordingly. when both are flat based bullets, it's pretty easy to eyeball and see how deep they seat. HB bullets complicate that a bit, but not overly so. Most HB bullets end up so the skirt seats a little deeper than a flat based bullet of comparable weight, but the HB "dome" compensates, added back some of that case capacity.
If ya took the flat based bullet and held it beside the HB, so the crimp grooves are even, and eyeball the bottoms, and you see that say half the length of the HB "dome" extends beyond the plane of the flat based bullet, yer gonna be so close to equal it ain't funny. NONE of our smokeless COWBOY load data is so hot that any closer a comparison is really needed. Now if the HB bullet sits a LOT deeper in the case than a flat based bullet, revert to starting load data and work up to get a satisfying load.
Specifically with trail boss, unless you use so much powder that the charge is compressed, squishing the grains, you can't have enough pressure to hurt anything. That you can eyeball by charging a case and holding the bullet alongside it. If the bullet is gonna smash the powder down, back off.