I've (nor two of my tappers who've tapped and made sheet in the South) ever thought sheet was worth doing until the price was over 100 baht per kg. Remember it is not just one litre/one kilo to compare. I forget the equation to get a 1.3 kg average mat, but you need considerably more than 1 litre of latex. Possible a 2/3 litre mix with water. Work it out, and unless storing (another problem) and playing the markets, 2 kgs of cup is a very similar price to a a kg of mat currently. Hence no point.