I can't post a pic of mine. It came out really nicely risen, fluffy and yummy - but not sour.
Here's what I did:
On th basis that it's the acid from the yeast that weakens the gluten and makes the bread flop (as learned by googling), I made a few adjustments to my usual recipe to reduce the contact time between flour and acid.
1. I prepared the leaven just before going to bed (75g water, 75g strong white flour, 1 tbsp starter). Next morning it was super fluffy.
2. I mixed all the other ingredients (without the leaven) together (400g strong white flour, 100g string wholemeal flour, 10g salt, 300g water), and left to stand for 1 hour to let the flour hydrate (bowl covered with cling film)
3. After an hour, I kneaded for ten minutes until it was nice and springy. Then I left it fir an hour to let the gluten relax.
4. After an hour, I worked the leaven into the rest of the dough. The difference in texture is very noticeable - the dough seems much less sticky than it normally would at this point - I guess because the acid from the wild yeast hasn't had a chance to attack most of the gluten yet. I left it for 30 minutes, then stretch and fold. Then left for an hour, and stretched, folded and shaped.
5. At this point, I didn't have the volume I'd like, so I put it in a warm (c 40c) oven for 30 minutes. I know a lot of sites say a slow rising in a fridge is best to develop flavour, but if it's contact with the acid that weakens the gluten, I thought a quicker rise might be advisable. Always left to rest with cling film over, to prevent it drying.
6. 30-40 minutes, I folded it twice, tucking the seams under, and put it back in the oven to rise a bit more. It flattened a little, but didn't completely lose its shape.
7. 30 minutes later, took it out of the oven, and preheat oven to 220C. Tucked the edges under the dough ball again to plump it up a little.
8. Popped into a hot oven for I think about 45 mins to an hour (lost track of time, I just kept checking til it looked nicely browned)
9. Hey presto, nicely risen loaf that kept its shape.