Get forged pistons. As a rule of thumb, use forged for juice or boost applications. If the hypers decided to go, that's an expensive problem. The cost of the forged pistons is cheaper than a new motor. As said, the hypers will work for awhile but forged will last longer.
Nope. Not for very long.
A bad tank of gas on a hot day while getting "it on" the freeway is about all that it would take before there would be issues.
One of my old engines was 10:1 hypers, and I got greedy.
I installed a 6 lb blow-through on it, retarded the timing to about 9 initial, 28 total, with an average fuel curve of about 11:1. It lasted about a year, then one day at the track......... #6 blew it's top.
I've heard of a few that lifted the top ring from too tight of end gap. I've heard of split blocks with hypers all in tact. Maximum Boost says they have some advantages over forged, and if you are not spinning them too fast, running high boost or too high intake temps, they are a good choice. Mine is going together with srp's, but is probably over kill. It seems hyper are usually stronger than head gaskets though. There are some guys on turbomustangs.com that are pushing stock hypers alot harder than you plan.
Well, everybody has an opinion so here's mine: they will be fine IF you do not go beyond 8 p.s.i. AND you install a boost retard unit AND you run 91 or higher octane. I've met several people with stock, (hyper pistons), 87-93 Mustangs and blowers running 8-9 p.s.i., boost retards, and hi octane that have engines that are runnig and racing with over 100,000 miles on them. Your air/ feul ratio is CRITICAL. I would not floor it until all of this is installed and your on a chassis dyno with a good wide band O2 sensor to check your ratio.
I'd go with the forged pistons, simply because the price difference isn't that much, considering the pain of a rebuild. When you decide to up the boost, you'll already be set, depending on what you've done with the rods & crank.