Thanks, I'm considering to get one smaller than 52t, I've found them down to 45t. I just got my Birdy with the special Sunrace 9-32t cassette (Capreo replacement). With that cassette it has more than enough high gear, so might as well get some more low gear, for loaded touring. It's fine for reasonably flat terrain, but there's no bailout for long >10% climbs. (My stock chainring is already on the outside of the spider, it would not be possible to mount it on the inside due to interference with the suspension pivot. This chainring has fat plastic chainguards on both inside and outside.)

First I have to consider alternative gearing setups, though. I was thinking 1x11 setup before, but it's clear now that this will rub on the chainstay unless I move the chainring outboard. And it's already further out than what it should be, for large cassettes. So two options remain: Either Alfine 11 (more or less enough range), or SA CS-MK3 / SRAM DualDrive setup with 9-speed 11-32 cassette (very good range). The Alfine setup is simpler, keeps the chain tensioner higher off the ground, and may allow a tighter fold, if the tensioner sticks out less than a derailer. By the way, they put a regular XT derailer on it, not the Shadow version, which might also have allowed a tighter fold. But maybe the shifter cable path on the Shadow isn't ideal given the cable routing inside the Birdy swingarm.