Ok, I have done it plenty of ways. You can cut a groove in the top/bottom. You can just edge glue it on there with nothing else
(if you plane it with your smooth plane first, and the top/bottom are smooth, the wood will break before that edge to edge
grain glue joint breaks). I have also dado'd them into the sides for fun. None have ever failed. I have never seen the baffle
move "significantly". I think if you cut a groove and glued it in there, even a 1/4", it would never fail. Again, I have amps out
there going on 7 years with edge grain gluing only.
I will say this, the actual original fender tweed deluxe has a
very thin strip of wood there. I make them about 1/8" larger.
I re-tweeded an original for a customer once (the original owner took the tweed off... smooth move) and man those front strips
were
thin. I looked at every inch of that amp, I did not see them being grooved into the top/bottom. Maybe they were,
or maybe they were on others, but I am almost certain this one was not.
As for cypress, I have built plenty of deluxe sized cabs from cypress... light, nice sounding, easy to work. If you are going to
dovetail them don't use a machine (jig + router) due to the tearout (or you have to use backer boards in all directions. I used
to hand cut them to avoid this, now I mostly finger join them.
Here are two extension cabs, the exact dimensions of a tweed deluxe (but the "strips" at the top/bottom
are not as tall as the original), and with no amp or cutout for an amp.
http://www.theairtightgarage.com/gallery/112x1.jpghttp://www.theairtightgarage.com/gallery/112x2.jpghttp://www.theairtightgarage.com/gallery/112x3.jpghttp://www.theairtightgarage.com/gallery/112x4.jpghttp://www.theairtightgarage.com/gallery/112x5.jpghttp://www.theairtightgarage.com/gallery/112x6.jpgI used to have a number of deluxe cab pics, I seem to have misplaced them.
HTH.