I understand why everyone says the 11 is worthless, but it's not.

Personally, I ride a 12 as my smallest cog.

However, in the past, I have ridden and used the 11. For training purposes, I would find a long open stretch, and stand. Of course my cadence was nowhere near 90, probably morel 55-80, but I would start higher, and continue going lower as my speed increased. Quite often I would end up in the 11 tooth cog. My math says that at 53x11,c55rpm will give you 20mph and 85rpm will get you over 30. So, no, the 11 tooth cog is not worthless...