So here's some updates... so far, the only real issues have just required some serious force and lots of sweat equity.
The lower cushions sit in the seats shown above... however, they've got a threaded rod with a jamb nut under them, and as you can see from the picture, it really doesn't look like anything is supposed to move. Except it does, of course! I had to remove the bolts entirely (the back one was lots of work, but not too bad) then insert a 7/8" bar in the hole and break it free from underneath with a 10lb. sledge. Now, many of you have never met me, so before any of the folks gunning for me get a chance, I'll describe myself: I'm 39, 6'2", 168lbs, and have all the muscle mass and tone that a cushy job selling stereos gives you, which is next to none. So imagine a few pipecleaners with a couple wads of chewed bubblegum and you get the idea...
Anyways, it was a lot of work, but the rear cushion adjustment seat finally broke free. It was entirely caked with who knows what, and it sure didn't want to come out.
Here's the pocket it sat in:
The front one was MUCH worse. When removing the adjusting rod, I ended up using a combination of big-ass pipe wrench and sledgehammer and spud wrench with 7' of black iron pipe as a breaker bar. Alas! The incredible resistance was a result of a completely destroyed section of thread just under the cushion adjustment seat. The threads for this seat will need to be re-cut, I hope... if not, then I'll have to drill it out and likely do a big heli-coil or something. Regardless, it took a ton of work to get the rod out. On to hammering the cushion seat free. It took three different days of slugging, and finally the only way it came loose was by removing the anvil from the hammer (heavy!) to clear a path so could 'baseball bat' swing the sledge. Using this technique and resorting to burning the surrounding area where the nasty cakey stuff was and scraping with a chisel, it broke free.
Here's what the cushion seats look like when they've been cleaned up and given a good coat of oil to prevent them from corroding any further:
Compare this to the picture BEFORE I got it out, and you'll get an idea why this was so nasty!
Here's a shot of the anvil and hammer separated:
I've had to start a pretty nifty collection of wrenches for this project, too! Here's the striking wrench I needed to break the jamb nuts free... not too often you get a chance to use a 10lb with a 10lb hammer! Not sure why these went out of vogue, as they made short work of every single big jamb nut on this ol' girl.
Finally, I spoke with a friend that has lots of hard rock maple... I need to take some measurements, then I start the helve!