The .530" mould should be just fine, Dan, however if you could find one, a .526" mould might be better, then use an 11oz. to 14oz. denim patch. Some guys have better luck finding thin canvas, in th e.022" to .024" thicknesses.
The hardened balls I used on moose in the late 80's early 90's were in paper ctgs. thus for me, the full sized balls at .682" worked. I found the hard balls VERY difficult to load if in patches, until I got a Tanner
15 bore mould at .677". It casts .675"/.676" balls of hard lead. These, along with the paper ctg. hard balls shoot identically to the larger soft lead balls, using the same 12oz or 14oz. denim patches.
Our own bobinthewoods also uses paper ctgs. for hunting. Dphar a tested these a while back, in his 16 bore and found them to strike identically to his patched round balls. This is
what I had found and wrote up a long time ago. Another old forum member, Roger, tested paper ctgs. for hunting and found them to work for him from .75 cal. right down to
.54 calibre. Below that size, I think the breech pressures are too high for the wadded up paper beneath the ball, to seal off the bore. Thus burning and inaccuracy resulted.
Your .60 cal. is perfect for this type of loading. Computer paper, now available in almost ANY 'weight(thckness)' should make rolling up ctg. that fit tightly in the rifling, an easy task. The paper
should be marked by every land when loading. Short starter not necessary as a choked up rod should be all that is necessary. We found if loaded this way, not loose as in
a musket, but tighter to the bore, they shot almost identically as patched round balls. Thus, no lube problems for up to 10 shots. Bob dips his paper ctgs. in lube. This also works and shoots
more cleanly as the lube softens the fouling left after shooting. If shooting 'tight' paper ctg. loads, I NEVER had a paper ctg. burn or ignite.