Randy Oliver in his Scientific Beekeeping website has recently published a report on his trials on extended release Oxalic Acid for varroa control. It would be a good product to reduce mites whilst honey is on the hive, before the main varroa treating period after the honey comes off.
http://scientificbeekeeping.com/extended-release-oxalic-acid-progress-report-4/
http://scientificbeekeeping.com/extended-release-oxalic-acid-progress-report-4/
May your bees read the same books as you do.