I have a Martin D-15 from when I was younger that I loaned to a friend and returned with a cracked head many years ago. It's sat in its case for all that intervening time but I thought I should go ahead and give it a repair and perhaps leave it up at the cabin so people can give it a play when the mood suits. It's worn from happy use and has character I like - it's time for it to be played again.

I was hoping for some advice on proper repair. Obviously my thought was to fill a syringe with hide glue and inject it into the cracks, then use a wooden handscrew clamp to really get some force down to close the crack. Easy cleanup afterwards, etc. Should I just mix it normal or thin it more so it "seeps" into the cracks better. Should I add any urea to extend the working time so that I can let it flow into the cracks better before I clamp?

I also have some System 3 epoxy with a medium hardener - about 30 minute working time. Since I'm using it for another project right now I was mildly considering it given how tenacious the hold is, but the cleanup on the mahogany seems like a no go - would hate to have to scrape it and work the finish again.

I'll remove the tuners before I glue it. Given where the cracks are I was just going to ignore the truss rod, but do you think I should loosen it too?

I've included pictures for reference. Any thoughts appreciated, just want to make sure I'm not missing something obvious that a luthier or someone more familiar with this work might see.