"I have recently purchased a Concerto bass bow from one of your dealers, David Gage in NYC, and here are my comments.
I had an early to mid 1900's Mittenwald carved student bass. I play in an orchestra, and this bass really lacked the necessary "punch". I upgraded my wooden bow to a Jean Grunberger Carbow last fall, and it certainly helped. In January this year I went to England to pick up my new Thomas Martin 5-string double bass, which was designed to be a powerfull orchestra bass. This bass is great for orchestra work.
I was fascinated by how the Carbow was better than my wooden bow, so I decided to try your Sinfonia and Concerto models. The Concerto really stood out for my bass, so I bought it. I can easily deliver a much more powerfull sound with less effort than any other bow I have played. I went to my weekly lesson, but I did not tell my teacher I had a new bow. He said "Your bass is really opening up nicely". That wasn't it at all - it was the new bow.
Tone-wise I found the lower strings deeper and the high G-strings notes cleaner and less fuzzy.
This bow does not play like other bows, so using the Concerto and a wood bow is only confusing for me. I am now selling both of my wooden bows, and I have bought a very cheap fiberglass bow to use for a couple of days when I get the Concerto re-haired.
I will be spending some time with spicatto bowing soon, but the amount I have tried it leads me to believe it will be fine. It will just take some adjustment of speed, force, distance off the strings, and closeness to the frog. This needs to be done with every new bow, so I expect this."