I seem to read that your a little worried over the battery drain, I would see the remedy for this with the purchase of a set of spare LSA batteries and have them charged before you go to the lake.
I have sailed a tug with the same motors for around 5 hours then changed to the second set of batteries and continued
I still take fully charged spare batteries when I sail my other tugs Tito Neri has two 12v SLA and one 6v SLA, the springer has a 6v SLA and the jet sky has a lipo (I can recharge the lipo by using a charger from one of the 12v SLA and also help out with others at the lake if they need a quick boost for their lipo's
Go to the lake and drive your tug hard then see how long your sail times are that way you will see if you have any need to change motors or find a way to increase sail times.
driving hard will give you the shortest run time from your batteries therefore it will be the best footprint to work from.