Don, In regards to the jig, I guess you will eventually figure it out, depending as to what you want to incorporate in it and what you want the jig to be useful for.
I am certain you are aware as to what the jig is mainly used for….
As far as "spacers" (between the frames), I believe you already have some shown on the plan in the lower area of the hull, these are part of your hull framing.
For those, you can refer to the links I sent you a few weeks ago in private: Uwe also sent some in in post 282.
Depending on how you want to proceed with the assembly of your framing and the jig you will be using for it, You may want to add temporary spacers at the top of your frames if you are afraid for the rigidity / solidity of the hull, and safeguarding the alignment of the frames during subsequent operations (like sanding): in a way, connecting / tying (like Dave said above) all the frames at the top. Although... There are different ways to achieve that purpose. Some modelers, clamp temporary planks or rails either on the inside or / and outside.
You may not want anything permanent added to the actual framing, but then again, if you do you could place them in hidden areas.
Other members may give you other ideas.
What I have done in the past is similar to what others do. Temporary battens at the top and across the frame. In this case, the frames have been extending, but you could also do the same on frames that have not been extended. In any case, it would still be possible to remove the battens later on: when one feels they are not needed any longer.
This is not "Le Rochefort" but you get the idea.
Once your framing has been completed, the keel, frames (including the small spacers on the plan) and the keelson have been assembled, these elements should be adequate for the rigidity of the hull: unless, of course, you plan on using a hammer and chisel to work towards the final shape of the hull.
So really, there should not be much to worry about in this regard. But this is only my view so other’s may differ.
If you want to add more spacers in hidden areas, it is totally up to you if it makes you feel more secure.
As for using a different wood for them, I guess, personally I would keep them the same as the frames ... but that would be a personal choice on your part.
G.
