Beating 'the bulge' and 'the handbag' - any thoughts?

Confession time...

I have been baking, but not posting pictures for a while. Too little time.

This weekend the loaves have been frustrating me.

The first bake was a version of Dan Lepard's Mill Loaf using 6 grains (White, wholemeal, spelt, rye and barley flours with some millet flakes)

from one side looks OK

[img]http://www.sourdough.com.au/gallery/d/4790-1/DSCN1385.JPG[/img]

but the bulge is obvious on the other...

[img]http://www.sourdough.com.au/gallery/d/4792-1/DSCN1387.JPG[/img]

(Not all bad, crumb is fine - taste is fantastic)

[img]http://www.sourdough.com.au/gallery/d/4794-1/DSCN1389.JPG[/img]

This bulge is something that I associate with loaves that have been in the fridge. This dough had a period in the fridge after mixing, then a few stretches and a couple of hours of rising at room temp, then 24 hours in the fridge after shaping. Dough was taken out of the fridge when the oven was turned on, and baked ~50 min later.
I think that the problem is that the top of the loaf cooks before the base, and there is still some rise left in the loaf, which can only get out through the still incompletely cooked base.
I associate this in particular with loaves from the fridge, and I wonder if it is more likely if the dough temperature is not even (outside warmer than inside?)

My theories to fix this include slashing deeper (more room to expand?), not allowing the dough to warm before baking (even dough temp), or leaving the dough longer out of the fridge before baking (risk of overproving though...)

any one else have this problem?

The other loaf was a try at King of Glop's [url=http://www.sourdough.com.au/forum//viewtopic.php?t=81]sourdough ciabatta[/url]

This is an 80% hydration loaf with 260% starter! I hand-mixed using Dan Lepard's technique

I haven't tried this recipe before, but have had a few goes at sourdough ciabatta, as well as other high-hydration sourdough white loaves (eg pane pugliese). The result inevitably seems to be a 'flying top' (also memorably described as the 'handbag defect').

[img]http://www.sourdough.com.au/gallery/d/4796-1/DSCN1390.JPG[/img]

This isn't a classic 'flying top' underprooved loaf, with a dense lower crumb and a big bubble under the top. It is more that the air bubbles form unevenly and coalesce, lifting the upper part of the loaf.

Is this inevitable with ~80% sourdough loaves?
I wonder if machine mixing would distribute the air better and avoid this? (I don't have a mixer, and only mix by hand, so it isn't really a solution, just a theory)

any other ideas?

Dom