Hmm, if you don't put something in the entrance you're going to have bees getting hung up between the hive and netting I would think. Also, when you start tilting/moving the hives to get the netting beneath them you are subject to have bees come out to see what's going on....have you ever seen a hive that has been disturbed at night....the whole outside of the hive can get quickly covered with a carpet of bees...creepy experience in the dark.
I would get some #8 mesh hardware cloth/screening and make a v-shaped wedge to slip into the entrance make it ever-how-wide the entrance is by about six inches...this is longer than what I usually use but it will give you plenty of mesh to staple down on the porch to keep it in place. Pinch the v-wedge together and slip it into the entrance...release it and the tension will pretty much hold it there. For insurance you can staple down the wedge if you want to. Once done, you can probably get by without the mosquito netting but if you still want to use it the bees won't be in your way now as you install it. Really, though, if you strap those boxes together and there is a little propolis on the box edges you shouldn't have problems with them slipping.
Gas up before you load the bees so once you start rolling you don't have to stop again until you get to where you're going. Make sure the bees don't overheat.
If you can, place them in the trailer on the side that is opposite from the vehicle's exhaust pipe. Depending on the type of trailer, the smoothest ride may be up front. Load the hives so that the frames are parallel with the road...that way braking and accelerating won't make the frames swing back and forth (they probably won't anyhow if they're glued down with propolis).
Best wishes,
Ed
