Need some help making a naturally leavened croissant.

I have spent the better part of a month trying to get this done. A Piece of Bread in tasmania has accomplished this and put their formulas up on a drop box. I have been following this feeding schedule leading up to the leaven for the dough.

Sweet build I found passes the float test at 4 hours in, but is suggested to use after 12 hours. All the temperature of the water I used ~30 ° C.

They have had 5 different types of recipes I've seen in the past 4 years and here are the formulas that I've noticed.

Same thing. Desired dough temp is 28-30 ° C.

Bulk ferment is 6-8 hours. Doing folds every 30-40 minutes (my place is pretty cool nowadays). Shaping them at 80g each. Baking 400 ° F and then doing to 350 ° F to finish.

Most results yield a very tight crumb. There is nothing wrong about the layering, standard croissant layering. I've done it enough times to get it down pat. But at this point the crumb is more doughy than spider web like. They said you can retard the shaped final product for 3 days. I know it is an issue with the leavening. I have done Tartine's croissant before but that does require commercial yeast to be added to it. But I'm trying to make it 100% naturally leavened. I've had slight success where it proofed maybe 30% but now I am at a standstill. I cannot get past that. Proofing is an issue of course between of butter leaking out of pastry past 27 ° C.

I don't know if anyone else could recommend any different recipes or perhaps any adjustments to the technique. I think a problem is how much initial enrichment there is in the dough. The fats in the cream is inhibiting it from rising or for instance in the "old" formula the butter and egg. I'm thinking of cutting back on the sugar by half, the cream by half and replacing that with water to keep the hydration around 50%. Should I add more water to make the dough more soft?

Any help would be great thank you.