IO-360 break-in and oil recommendations?

Our normally-aspirated Arrow IV is currently in the shop getting a Lycoming
factory rebuilt ("zero time") IO-360-C1C6 installed. This is the first time
in my 2000 hr. flying career that I have ever had to deal with an engine
break-in, so I would welcome advice from the group.

Lycoming apparently recommends operation at 65-75% for the first 50 hours
"or until oil consumption stabilizes." This is to assure proper piston ring
seating. They also recommend use of straight mineral oil during this
period, and we plan to run on Aeroshell 50 weight mineral oil. Anybody
suggest otherwise?

On our old engine, we ran single weight SAE 50 (Aeroshell 100 AD) year-round
with excellent results. (we fly out of PAE, where it rarely gets very cold
in the winter.) In around 2150 hours of operation (i.e. well past TBO), we
never had a major problem. Even now, we are changing engines on general
principles, not because of any indication that anything is wrong.
Continuing to use Aeroshell 100 AD (after break-in) is therefore rather
tempting, but it seems that everyone is extolling the virtues of
multi-viscosity, semi-synthetic oils. These contain an anti-scuff additive
which is required on some larger Lycoming engines. Apparently, Lycoming has
no problems with the additive in smaller engines like the IO-360, but
doesn't require or even specifically recommend it. Any thoughts from the
group on oil selection for general (after break-in) operation?

--
-Elliott Drucker