Why is my SD crust thinner and less crisp than I would like?

Hello,

        I've spent a lot of time on this forum in the past and learned a great deal. Coming back to see if I can get some comments on why my crust is a bit thinner than I would like and also softens up more than I would like after being out of the oven for a few hours. I'll give a quick overview of my process below. I'm aware my technique/approach is unusual. This timing works well for my schedule which is why I have adapted it as such. 

1) At 9:00 PM start a loaf of dough using a stiff starter (65% hydration) that has been fed six hours prior and has at least doubled, very healthy. I autolyse 425 grams of bread flour and 75 grams of whole wheat with 380 grams of 90 degree water. Wait 30 minutes and add 100 grams of said starter. Add 1/2 Tbsp salt. Mix thoroughly by hand and cover for 30 minutes. Do three sets of stretch and folds at 30 minute intervals over the next hour and a half. Cover at approximately 11:30 and leave on counter (68 degrees) to bulk ferment overnight. 

2) By 8:00 the next morning it has doubled/tripled. I do a pre shape, wait thirty minutes, do a final shape and place it in the banneton. Cover and let final rise for roughly an hour. Bake in Lodge DO for 25 minutes (500 degrees) covered, remove lid and bake 20 minutes longer. 

3) On occassion I will start a loaf in the AM and work it over the course of the day and pop in the frig overnight as a cold retard. This loaf turns out similarly to my overnight on the counter loaf, maybe a bit thicker,crisper crust? 

As my photos show my loaf is not very open crumb and I just purchased Trevor Wilsons book on Open Crumb to try to get to the bottom of that. I've tried in the past but with limited success. So, I would like to see my crust a bit thicker and for the crust to remain largely as crisp as when it comes out of the oven. For what it's worth I always wait two hours at least before cutting a loaf open. Interestingly a frieind of mine who I gave some starter to and showed her the ropes a bit and follows virtually my exact timing and technique is getting loaves with a thicker crust and one that remains crisp. Her's also is a fairly closed crumb. 

Anyway, any thoughts will be greatly appreciated. 

Cheers,

            wvdthree