Thanks! That's what I needed to know.
I had a 750 back in the day that I dispensed with the electric start on and it had a very small (size of a pack of cigarettes) combined rectifier, regulator, and battery. I have no idea who made it but I do recall that in 1971 it cost me somewhere around $300. It worked just fine but you had to turn on the ignition and kick right now, not later. Obviously it had some sort of small internal battery to excite the alternator fields, but if the light was on it didn't last long. That wasn't a problem, I've never owned a Honda that did not start immediately, even cold.
On the bike I'm doing now I would like to keep the electric start but completely hide the battery, hence the quest for the smallest possible. However if I can't hide the battery, and it doesn't appear that I'm going to be able to, then I have to find the most attractive way to put it in the most sensible place possible. I am keeping one thing in mind - gel cells do not have to be mounted upright, hidden or not.