I have been growing these in NW Oregon for the past four seasons. I originally got the seed from seedrenaissance.com and started with over 100 seeds. I didn't have any reds, but a mix of mostly brown/yellow and white of various shapes. The darker onions have proved to be much more vigorous and have stood up better to my selection.
I store them inside through the winter on a kitchen shelf and only plant out bulbs that make it through to spring without sprouting or getting soft in my conditions (8+ months stored at room temperature and exposed to light). They are planted in April and I generally harvest in August. They have been one of my most hardy and reliable crops, despite some neglect.
Really my main selection criteria has been storability. This has favored more uniformly round onions with skinny stems. Every year I have grown these, a large portion went to seed and none of those bulbs were saved to plant out the next year. Even my fourth year (2018) after selecting out everything that flowered, many still flowered. I ended up just yanking them and leaving them in the garden where apparently many have survived the winter and are starting to grow. I included some photos of what I currently have stored as well as what has been left in the garden overwinter. There are a few clumps of small onions that I missed when harvesting! Only a small subset of the seeds I originally started with have reliably multiplied without flowering. I haven't saved any seed yet and would suggest that bulbs be grown out for at least a few years before collecting seeds to select against a strain of onions that produce seed every year (and make poor storage/multiplier onions). This year I may try to select out bulbs that don't multiply or only divide into two. My ideal multiplier divides into 3-6 medium onions. The ones that divide into 8-12 bulbs are just two small to bother peeling in my opinion. The very large onions don't store as well and only come from single or double divisions. I will try and save some seed this year if anyone is interested in adding seeds from my selection into the mix.