For me, they are great. I have a Simpsons Trafalgar T3 and an Omega 1.0 and they are so good, I've PIFed my other brushes (Omega Boars and an Omega Silvertip) to my kids. These are my only brushes going forward, and I'm quite happy with that.
My understanding is that he will set his own knots in his own handles, so you could check his web page or Etsy pageI wonder how to communicate that to him when ordering.
I’ve noticed that Simpson synthetic brushes do need a bit of a break in period. But then again I don’t have many synthetic brushes so I don’t have much of a point of referenceThe Simpson had a bit of a learning curve in that it’s the only synthetic I’ve encountered that has a break in period.
If you are looking for a brush with the entire fibers being very soft, as @Omega48 mentioned you would want a Mother Lode knot and I don't think diameter would matter at all as it is a very sofy floppy knot as most have described in the past. My next suggestion would be a brush with a TurnNShave Angelhair knot in it set with a high loft or lastly, ultimately what you may need to look into is a Wald A1 knotted brush. I have the 27mm Calyx which I've found to be almost too soft and much softer than my Angelhair knot. They also sell the A1 in 29mm and 18mm variations too. If its worth mentioning I too am a full time face latherer is why I make these recommendations...Is there a currently available synth brush that is as soft as the L'Occitane made by Plisson? I love this one for face lathering but the handle is run down so much by now (I tend to throw them on the floor when in fact I want to shake out water after cleaning) that I'm in the market for a new synth with very soft fibres. I own an unholy amount of synth brushes now and none is as soft. Not even a regular Plisson synth. That's so disappointing.
I read the post before mine about the A2S and wonder if this is it? Or maybe one of the PAA brushes? I like the look of them very much, especially the Solar Flare one.
The reason why I recommended the 30mm knot is because I have a 26mm and a 30mm. The 26mm is as floppy as reported by other members. The 30mm is super soft and gentle but it is not floppy at all.... as @Omega48 mentioned you would want a Mother Lode knot and I don't think diameter would matter at all as it is a very sofy floppy knot ...
The Mother Lode is indeed amazing. Cloudlike softness, dense without hogging lather, splay without effort, and they hold water well. However, the last Mother Lode I got from Boti was a shedder. It is the only synthetic I've owned out of probably two dozen that dropped hairs on regular basis. I recently bought Mother Lode replacements from Oumo via AliExpress and they are non-shedders. And they cost less than $10 shipped.I would recommend trying the amazing Boti Mother Lode. Possibly in 30mm. On Amazon or AE.