I can't say for positive, but today at 75 mph I was reading just about 2,900 rpm in 6th gear. When I ride I ride two up and even if I slow down to 55 or 60 mph without shifting, I can ease on the throttle without trying to lug it, and it increases in speed very quickly. I have an '08 SERK.
I have no problems with the speed upper end, although maybe a few more revs wouldn't hurt anything.
All this talk about rear and front sprockets, don't you have to do a complete primary removal to change out the front output sprocket? The rear sprocket, if you can maintain your stock belt, would be a good choice. I'm not certain but the belt pitch looks to be about 3/8" or 1/2". If that's the case two teeth will move the axle approximately one tooth pitch closer to the trans. Then you have to recalibrate the speedos on the '07s or '08s.
I still think the better option is the Evo Industries clutch hub with the original starter sprocket and a 49th clutch sprocket. I comes with the new primary chain and you don't have to pull the inner primary cover off. You also don't have to fuss with the speedo as it's all upstream from the trans. I think the dollars are a bit more, but the hassle factor may be less overall. The clutch sprocket and primary chain kit is about $324.00 and I'm not sure what the rear sprocket costs for the rear wheel. Doing this is about a 5.5% increase in low gear for a better take off and less clutch slipping, especially two up. If I had this conversion my 75 mph rpm would raise from 2,900 to 3,060, not a lot but enough probably to help out at slightly slower speeds.
I just read the AMI review of the Tri-Glide and one of the things they said in that was that they had to slip the clutch on take off a bit more than they would have thought. Now if any of the HD bikes need a lower low gear it's the Tri-Glide.
I could see the gear ratio as a benefit if it were a car because they could tout the "increase" in mileage the extra taller ratio provides. But with bikes I don't hear anything about C.A.F.E. mileage requirements, so why does HD insist on making the rpms so low on these bikes? Is it emissions related too?