Well having paid the money and bought the product I have put it onto the hive with the highest varroa load (no DWV or CBPV but noticeable phoresy started to be observed on bees during inspection) and followed the instructions to the letter other than to leave the OMF open. Since fitting early this morning the temperature is down to about 13 and we have wet stormy weather. As this hive is a good 20m from the rest of the apiary I intend to see how things go and treat the others within the next week or so. I apricate your supposed to treat together but given the distances between and current bad weather drifting is going to be minimal. If I notice anything drastic I will report back