I'm not gonna get into the middle of the fight of what is right or wrong, etc... but personally I wouldn't hesitate to use 60gr pyrodex with a little better bullet, setting up a youth load. The 240 xtp should be fine, 240 deep curl would be even better - but they are tough to find.

I don't think that a load like that would be unethical at all, as long as kept to relatively close ranges - which is likely what a youth would be doing anyhow.

fwiw, my brother in law uses 70gr goex real black in his sidelock with 260gr speer jhp bullets. (the one's knight sells) Every deer he's ever shot has been dead, no issues at all. Most of the shots have been under 75yds, I know he shot one right close to 100.