Too bad you didn't have much wind in the Holder 14's. They can be pretty fun with some wind.
If I may, I think you are putting the cart before the horse. Setting a 'must have' length is a bit arbitrary. You should be looking for a boat that will make you happy not a boat of some arbitrary size.
Size (length) is of course a factor as stepping the mast on some boats can be a bit of a chore (it is on my 19' Lightning) that may discourage you from using your boat. My suggestion is to actually get a ride on some of these boats before you decide to buy one. Then you can decide if the boat is right for you.
Another consideration is what boats are actually available in your area. I mentioned the Beetle Cat which seems to be largely a New England/East Coast boat (I found none for sale in CA). Do you really want to be shipping or hauling a boat all the way from Oshkosh or wherever?
I found 2 Lightning racing fleets in CA (Mission Bay & SF) where you might be able to hitch a ride as crew.
http://www.lightningclass.org/Fleet/districts/californiaDistrict.htm
The Flying Scott is also a very fast, stable boat as mentioned but I'll leave finding owners of this model to you.
Some of the Lightnings that people are selling are kind of expensive and likely come with all kinds of sail shaping controls you did not have on the Holder 14'. That said, I got mine for $1k with trailer - fire sale. I would not describe it is a beginners boat but even I am growing into how to use all the controls.
You might consider the 'Snipe' which is an older 1 Class racer and likely has simpler rigging.
My main point: Try before you buy. Even if you have to pay the owner something to set up and launch the boat.
You should also try to get a ride on a Catalina 22 or similar boat. These are very stable and cannot tip over (easily) and you can sleep on it.