I agree with the advice to work with a qualified rigger.
Frankly I don't get the advantage of doing this. Presuming you have a relatively modern roller furler on the headstay, it is much easier to just take it down and put up a storm sail before storms roll in. And this approach doesn't require you to furl the big headsail every time you want to tack it just to get it passed the second stay.
Changing head sails on roller furling when single handed is not very easy. You need to deal with the halyard and feed the sail at the same time. It is a lot harder than with hank-on sails. The luff tape sails are also harder than hank-on sails to flake properly singlehanded, especially while on the boat.
With a solent stay the inner forestay is removed when you use the roller furling sail. On a modern implementation the solent stay will be a low stretch synthetic (like Dynex Dux) that is stored alongside the mast when it is not in use.
From my point of view the solent stay gives me the ability to use my 135% genoa most of the time (it is the right sail when winds are 15kt or less, which is typicaly here in Seattle) with all of the ease of use of roller furling. In higher winds I could deploy the solent stay and run a 100% jib and then when it is time to double reef I can hank on a storm jib.
It is possible to roll down my 135% genoa to a 100% jib, but even with a high end furler and foam luff panels the shape is not as good as a properly cut 100% jib.
Without this setup I have trouble pointing much at all in winds over 30 knots. The boat gets overpowered until I reduce sail, and the sail shape of a 50% rolled up jib is too poor to point. Running on main only works best, but my boat doesn't point very well on main only.
The solent stay is still enough work and cost that I'm heavily considering having a heavy weather 90-100% sail (that can be rolled down to 60 or 70% pretty well) cut for my boat and changing sails on heavy air days.