It might be useful to remember that Everclear is not pure ethanol.

At 190 proof (95% alcohol), it contains about 5% water, which is probably enough to affect stove performance. Over the years, I've read backpacker reports about certain denatured alcohols that seem not to work very well in stoves, apparently because of their water content.

One example is Parks Denatured Alcohol, which, according to the last MSDS (Material Safety Data Sheet) I downloaded, contains:

Ethanol 87-92%
Methanol 5-10 %
Methyl Isobutyl Ketone 1-5 %
Ethyl Acetate 1-5%
Rubber Solvent 1-5%
Water 5-10%

Despite the high ethanol content, my recollection is that Parks performed poorly in most alcohol stoves, probably because of the water. Admittedly hearsay evidence, but a possible contributing factor for your results.