Well I'll answer my own question here and say I'm sure it's not a problem.

For 3/4 cap, the temples are already part of the template due to the size,
and then the sideburns would be to a 3/4 cap like temple flaps are to
a topper, i.e. just a piece hanging down. It would be smaller for a 3/4 cap (sideburns)
than temple flaps are to a topper, all pretty managable. For people concerned
about the transition to a full cap (like me) who just don't like their temples/sideburns,
I think this is a step of the transition to full cap, where maybe the entire step
may never be necessary.

Just a way of using some of your own hair on a full cap and I do not think I
even need to go further down the back than i do with my topper, so the
extended coverage is mainly on sides/sideburns/temples.

Looking so forward to it!

AG