minikinminx:I've been a well fitting 3 mil steamer under a 7 mil farmer john, it does seem to make a significant difference in water. I was able to add the extra layer comfortably and without adding any additional weight, but a better fitting FJ may have given me the same results.
You were overweighted. A 2mm shorty might be a absorbed in a rounding error but a 3mm fullsuit will move the needle. If you were able to remain down throughout the dive after adding the 3mm you were carrying extra to begin with.
Pete