Flying Free-luff sails (Spi or A-sails) is not to be taken lightly when singlehanded or shorthanded
offshore (or inshore, for that matter) - I personally can't see any merit in them other than when
racing.
I agree with all those who say that a prevented main* and poled-out headsail is a great option, even midocean. If the sails are well trimmed (pole right length and height,
mainsail nicely cut and boom pulled down by a powerful vang), rolling is NOT generally a problem.
If the genoa is the same size (within say 10%) as the main, and the above conditions are met (and the pole is strong enough) this can be the most stable setup of all.
For instance, if you've already gained enough experience in less challenging situations, set up as above (under full main), you should have a fighting chance of being able to hand steer DDW through limited duration squalls with gusts approaching 40 knots true (this is NOT a recommendation: do not PLAN to do this: it's a coping strategy if cornered by circumstances changing too rapidly !).
Provided also that the
hull has good lines, the vessel is not too heavy laden, and the
rudder is deep and efficient.
Handling the genoa is definitely safer with the recommendation from at least one previous post that the pole is set up independently of the sail, with its own topping
lift, foreguy and afterguy.
Not many people know that, provided you're not already overcanvassed, you can even heave to (not as a heavy
weather tactic, but in order to deal with a 'situation' -
gear failure, problem down below, injury ..... without doing
anything to a poled out headsail. (Assuming the pole is of the strength it should be, for you to be potentially using it singlehanded in the first place).
You can also do this, if the pilot or
self steering has failed, and you need to (say) put a reef in the main. (except for those boom
furling systems which will cannot be reefed with the boom well out - these are not a good choice for single-handing)
To do this: Gybe the main to the same side as the headsail, leaving the mainsheet long enough that the sail is at least as far out as the headsail,
harden the preventer (it won't
work if you omit this step) then come gently up in to the wind. Leave the
wheel lashed hard to
weather (ie, trying to round the boat up.)
Those who have done some windsurfing can think of this as analagous to a two-masted windsurfer, preparing to get underway but prior to sheeting in. The windsurfer will remain stable in this situation indefinitely, as will a 'proper' sailing vessel.
Contrary to what you would imagine, the sails cannot flog. Flogging requires that the clew has some freedom to move side-to-side. In the situation described, both clews are held solid, relative to the boat.
Rolling, because of being beam-on to the seas, is also not the problem you might expect, unless you're in a boat which is
really beamy at the waterline. The sails in this configuration are still surprisingly resistant to being rolled to windward, and the boat will maintain a very constant heading - generally yawing less than the 'backed headsail' hove-to option.
*(using a system where you can safely ease the main across into a gybe - if the boom is not strong enough to do this easily with a siderail vang, you'll should think about a combination of a classical end-boom preventer and a mid-boom brake)
NOTE: I have responded as though you were
singlehanding, because realistically, with a crew of two, you will be handling the boat singlehanded virtually all the time, and even in emergencies, you can't rely on the other person being fully functional. It can be stressful travelling as two, if both parties are not confident on their own.