I had a 309, and now have a 315. Close enough? Aside from docking, I don't see it as being any more difficult to single hand than a Seaward 25.
An improvement I made to my 309 and will likely make on my 315 is to bypass the cleat for the Genoa furling line, and add...I'll do my best to explain it....a block and a cam cleat gizmo that can be attached low on your Portside stern rail down low to the deck. I hope that makes sense. Garhauer Marine sells one for about $70. This makes it MUCH easier to make adjustments or roll up your Genoa from behind the wheel.
I guess one other thing I did on both boats, is to have a winch handle mounted about a foot from the Genoa winches and the mainsheet winch. I get PVC plumbing pipe large enough to accommodate the handle, cut it down to the appropriated length, and attach it to the stern rail and the support for the dodger. They seem to hold up to UV, they're cheap, and they look fine. I drill small holes in them and thread some light double braid line through the holes to make the attachments. Having the winch handles exactly where you need them makes a noticeable difference. Oh...the lettering that's on the PVC pipe comes off with acetone.
Everything else on these boats is single-hand ready. Have fun!
P.S.
The one thing that's a little inconvenient on these boats is the traveler. Located forward of the companionway hatch, it's not exactly handy from the wheel. Unless you have ten foot arms. Generally, what I do is before I come about, I release the car for the traveler and let it slide down the track to where I'll want it to be after I come about. That screws up the set of mainsail, but not enough to make as real difference, as I immediately return to the wheel and turn the wheel to come about.
I've used the auto tack feature on my autopilot just to try it, but I prefer to turn the wheel myself when tacking. Not saying one or the other is better, but I prefer to do it myself. Turn wheel, wait for the right time to release the windward Genoa sheet, and once the bow crosses the wind, I lock the clutch on the wheel and rapidly pull in the Genoa sheet on the new windward side. Once I re-engage the auto pilot I can fine tune the Genoa. Of course, the main takes care of itself.