Ok, everything looks to be fine. It folds OK, nothing is in the way. Once unfolded chain is on the chainring, no issues. Gave it a try today. I noticed that when I’m on 53t chainring and approaching big cogs on cassette while climbing, drivetrain becomes very quite and solid once I switch to 39t small chainring. Probably because chain line becomes straight. Also could climb very steep hill while seated on 39t chainring and 32t cog. Very pleased with this setup!

Also decided to give a Trigo front carrier block a test. Loaded 9kg on my Brompton bag and tried to ride. Couldn’t go 10m as front was wobbling like crazy. Don’t know what it was, an adaptor that isn’t firm enough or Birdy’s frame/fork design that is not supposed to have this weight on the frame in this anchor point. It probably should be fine for lighter bags but I think I’ll remove it. Will install front front riders if I’ll ever feel the need to use front panniers.