[OwenM]

It seems the people who noticed a loss of top end with sprockets installed are R1100 owners.

My R12RT and R12GS both make more power than stock over about 80% of the rev range with sprockets installed, about the same as stock for 10%, and maybe a little less than stock for about 10% above 7000rpm. I say maybe because I cant actually notice any loss.
The flattening of the power curve may make it seem like the top end is deficient even if its not.

The R12S has more aggressive cams and is tuned for more top end power. Installing Lennies sprockets on the R12S is more likely to incur a noticeable loss in top end but also potentially provide greater gains down low where the S is not strong.

It all comes down to what people are after. If maximum performance above 7000rpm is of greater importance then the 1500 to 7000rpm range installing the sprockets is obviously not advisable.

I would suggest that if power above 7000rpm is what floats peoples boat, an air cooled flat twin BMW is not the ideal tool.