Reason for OTOW penalty according AOL C-1-QNW-MGB-89_L592
dated December 21,1989.
" At temperatures below 6ēC the fluids may not completely flow off the wing by lift off, and this can result in a small increase in drag and/or reduction in maximum lift."
Beside that, I think that AOL recomendations concerning penalties, no longer aplies cause of right now deicing fluids approved by the AEA must comply with fluid´s flowoff characteristics test criteria.
REGARDS.