Hey Norm,
I have 8's on my 298, 2100's, and 2101's. I also run an 8 on my 3120. However, I am not running real long bars. I have a 32" on the 298, a 34" and 36 on the 2100's, and 36" bars on the 2101's. The 3120 wears a 42". All running full skip, most of the time. The 8 pin's give you noticeably more chain speed, but do take a little more power. That being said, The 2100 series saws still pull with no problem, and no shortage of power. The only time I have noticed a little lag was with one of the 2100's (36"), in dry white oak, full 36" cut. I have run the 2101 with a 42", and it does fine. The 3120 pulls through just about anything, and plays with the 42". If I were running a 42" on the 2100's, or 2101's all the time, I would probably run a 7 tooth. Just my 2 cents.
The 2100 series saws are animals, and are extremely tough saws. I am currently rebuilding the first 2100 I bought, that I have had since 1983. It has cut an unbelievable amount of firewood.
The 2101"s seem to run even stronger.