What is possible?

The current boat I am working on is yet another iteration of what I like to think of as my version of the perfect bay boat, bay kayak, that is.

One version of the bay boat, a canoe with outrigger for stability. However, too slow for long distances.

The perfect boat, for my current purposes at least is a boat that is fast enough to do a six mile bay crossing in a reasonable amount of time.  The boat also has to be car-toppable and be human powered, that is propelled by oars or paddles.  By reasonable amount of time, I mean that I want a boat that I can paddle at 4 mph.  Average speed will be less due to aimless drifting and beverage breaks, but if I can push the boat at 4 mph without making it an athletic event, then I will be happy. The boat also has to be reasonably stable, that is stable enough that I can stop and rest or take a photograph without having to do fancy bracing with the paddle or put another way, a boat that does not require my constant effort to keep it upright.

The outrigger canoe afloat.  On flat water, it is stable enough to stand up in.

Of course, speed and stability are conflicting requirements in a boat and so they need to be balanced for the proper compromise. The canoe with outrigger pictured above is not a proper bay boat because it is too slow. But it would make an ok fishing platform. In any case, I am sure that the boat I am currently working on will be a reasonable bay boat.
Which brings me to my main point, namely, what is possible?

San Francisco, six miles distant.

What I would like to do is periodically paddle over to San Francisco, in a boat that can do the trip in an hour and a half each way.  If it is summer and the trip over is started before 11, there will be little wind.  The trip back on the other hand will have lots of wind, although it will be a tail wind, 20 to 25mph being common. So if I start at home, drive to where my kayak is, launch it, that is half an hour added on to the 1.5 hour trip over for a total round trip of 4 hours.  If we add another hour for lounging about at the destination, perhaps to have a cup of coffee, then the whole trip will be about 5 hours.  If we add another hour for dallying along the way, then the total trip will turn into a 6 hour event, that is, 6 hours to go to San Francisco for a cup of coffee.
And once again, we have to ask ourselves, what is possible?  It isn't the physical constraints that make a paddle to San Francisco for a cup of coffee such a rare event.  It is more a matter of how much time it takes.  I can take a one hour paddle by launching off the boat ramp which is half a mile from my house. Total elapsed time for launching and landing is half an hour. So I could do a one hour paddle in 1-1/2 hours.
I do in fact do the short paddle near my house fairly often and the paddle to San Francisco only rarely.  What is possible in part has to do with how much time I allow myself for paddling.  When I think of the people whom I know that do more extensive paddles, they are invariably single people with few responsibilities other than to themselves.  So what is possible?  Perhaps what we allow ourselves.