Digital luggage scales will read up to 25kg+. Using them one side of the hive at a time will allow a hive of 50kg to be weighed and that should be plenty to reassure you that all is well regarding stores through the winter. No need to be super accurate. Hefting is a quick and easy way for a rapid assessment. To link to another recent posting on marbling honey I just let the bees have all the ivy honey having fed about 15kg sugar syrup per hive after taking the summer crop off by end of August. Mine are stuffed full of stores as of yesterday and doubt if fondant will be needed this side of February - if at all this year. I'll keep hefting though just in case. Cold doesn't kill bees but starvation certainly does.