F brush was used by us for most stuff over the last few years of brushed racing....we did use 4499 and 767 on occassions, but they were not usually run of the mill......Peter did lots of weird stuff with brushes, sometimes I think he may of had sex with them.....
You could not of paid me to run the Peak/Orion brush.......
All brushes suffered from good and bad batches. We had a batch of 4499 that were amazing...luckily I ordered 5000 of them, so we had a good stock on them.....same with Fbrushes....they had one amazing batch, one terrible batch.....then the rest were good brushes.
A 768/769 is a 767 with a hole or cut (can't remember which was which)....100% same compound though.
Later EddieO