Choosing pot sizes for BM-style and BIAB.

I'm probably going to make a compact, full-volume mash setup to be used both as a pot-in-pot recirculating system (like the braumeister or grainfather), and also for simple BIAB brews. I've mainly been a 3-vessel chap until now, with just a bit of BIAB and no Braumeister/grainfather experience so wanted to check things:

My aim is to 'easily' do batches of 23L at up to 1.080 OG in the FV - i.e before any need to top-up, double mash or struggle to avoid overflows. It would also be good to do occasional double batches of lower gravity, with perhaps a bit more faffing about required. But looking around various forums on the BM and BIAB, claimed efficiencies for full-volume mashing vary widely, so its hard to call what size pots are needed.

I already have some Bergland stock pots which could be used. I calculate that (for grain pot/tube and kettle respectively), 33L + 50L would be fine for single batches but 50L + 70L would be more comfortable with high gravities and 'perhaps' adequate for normal gravity double batches. For the BM users out there, does this seem a good choice or would that be pushing things for double batches? (I do have a 100L pot but its bigger than I really wanted to use).

Cheers
Kev

I decided to stop researching efficiency claims and instead look at what volumes, grain-bills and gravities people were getting.

I've concluded that yes, a 70L and 50L are the way to go, seeing as I already have them. The extra wiggle room appears to be worth it, would even permit occasional double-batches (perhaps with a bit of topping up/sparging). Which seems to suit my needs admirably. Though 70L & 100L would be tempting were I intent on doing double batches frequently, it seems a bit excessive for normal 23L batches

Cheers
Kev