Zeedman
Garden Master
Two beans per pot are quite comfortable together.
I thought that pot sounded a little large...I like this thought, especially with climbing beans. A 90 cm pot is about 3-1/2". That should give enough room for two plants if you leave them enough room between pots when transplanting them outside. Just need to think about it a bit.
The size 32 peat pots I use for pole beans are 2.5" square, and 2.25" tall. I started planting 2 beans per pot in case one didn't come up, and thinned down to 1 before planting. Then after losing a few plants one year, I had the idea to thin some time after planting, in case something damaged a seedling... and of course, forgot to thin later. Ooops. The bean pairs were spaced 12" apart, and to my surprise, did fine at that spacing; so I've continued that practice. From one 8-pot peat strip, I can potentially get 16 plants - which allows more beans to be started per tray. There are some very vigorous beans that I still thin to one per pot (Kentucky Wonder, Bird Egg #3) but pots of 2, spaced 12" apart in the row, has become my new default.
At 2/pot, bean seedlings are not crowded up to the point where they have their first true leaf. If held much longer than that, I have to thin them to 1/pot to avoid stunting. I gradually thin direct seeded beans to 4/hill, then 2/hill when runners appear. That 2-stage thinning paid off this year, when deer ate some plants from several hills - but left at least one per hill undamaged.