Honeyed Spelt & Oat

Hello, TFLers -- I'm a longtime lurker and relatively new sourdough baker. I've learned a lot from this site and am hoping to start logging some of my bakes here to learn even more from some of you!

This is my most recent bake, the honeyed spelt and oat from Sarah Owen's Sourdough cookbook. I've tried a few of her breads and have been quite pleased with the results. I mostly stayed true to the recipe, though I swapped out half the bread flour for AP just because I prefer the texture. I also autolysed the flours, soaker, honey, and water for about half an hour before adding the leaven. Overall I probably added an extra 3-5% water.

This made two small-ish loaves; the first I cut into about 5 hours after baking and it was still a little gummy. This one I waited a full day and the texture had set up quite nicely:

Things I would do differently for the next bake:

• Try to stretch bulk a bit longer. The dough felt aerated but I think I could have stretched it another 1/2 - 1 hour. I had quite massive oven spring, which I think is from slight underproving (?); please correct me if I'm wrong!
• Let dough sit at room temperature a little longer before refrigerating overnight. I'm finding I prefer to bake straight from the fridge because scoring is much easier.
• Bake a bit hotter. I should also take the internal temperature just to see where I'm at. These were 5 minutes at 550 dropping to 500; 20 minutes at 450; 15 at 430. Next time I'll keep it at 450 the whole way, I think. 
• Definitely wait the full day to cut! I was surprised at what a difference it made.

Overall I very much like this bread, particularly toasted with jam!