Remington 1858 ASP, Uberti, or Pietta...I carry mine with 6 chambers loaded Holy Black, Cap, and Ball, hammer in the slot.
Maybe you already know this, and if so, I apologize, but:
Carrying a percussion revolver with 6 charged and capped and the hammer down on the between-chambers safety notch is less safe than carrying with 5 loaded and the hammer down on the empty chamber regardless of the revolver design. Here's why:
With the hammer down on the between-chamber safety notch the bolt is resting on the surface of the cylinder, between the cylinder stop notches. In this condition the only thing keeping the cylinder from rotating into battery is the hammer in the safety notch on the back of the cylinder. If the hammer is pulled back inadvertently it only needs to move a short distance until it clears the notch for the cylinder to rotate. In addition, the cylinder needs to rotate only 30 degrees until it's in battery, and it will stop in battery because the bolt will engage a cylinder stop notch. The hammer will then be free to fall on a charged, capped chamber.
With the hammer down on an empty chamber the bolt is engaged in a cylinder stop notch, and both the bolt and hammer are resisting any cylinder rotation. If the hammer is pulled back inadvertently, it must move back substantially further to clear the nipple recess AND to cause the bolt to move free of the cylinder stop notch before the cylinder is free to rotate than in the above case. Also, the cylinder needs to rotate twice as far (60 degrees) before a charged and capped chamber comes into battery.
The latter case is safer by simple geometry; whether its enough safer to warrant not carrying that extra round is a matter for personal choice. Frankly, considering the possible consequences of an inadvertent discharge, I believe it's worth it. But to each his own.