My .02 is the Shavemac 501....
Overall brush height: 106mm
Handle height: 46mm
Brush loft: 60mm
Knot diameter: 23mm
View attachment 6945
I have the Silvertip in this size brush. Great brush, but I wish it had a bit more spine. The knot is dense and the loft is just right. Holds a ton of water also. IMO - I think the Finest would fit your requirements. The one pictured is from Vintage Blades - $69.70
I'm learning the brush lingo, what do you mean by a brush having more spine?