As more overhead casting is part of getting ready for the THCI, I have tried it with a number of different lines. Seems to me one can overhead cast almost anything, while line design dictates the style for change of direction casting with a D loop.
I notice that RIO
does not mention overhead in their Outbound promo texts, but that is an easy line to use overhead, in the surf, for instance. I think it was once marketed as such. It has an under 40' head length. Longish front taper.
Intriguingly, when one searches for "overhead" on the RIO
site, up pops their Switch line, which, for me was not as easy to overhead cast.
Two years ago at SOR, Nick Curcione, famous for surf fly fishing, was demoing a Skagit head overhead for the surf.
Simon does a fine job with this topic in the "Understanding Spey Lines 2013" on the RIO
It will be interesting to see what others say on this.