This is a bit Heath Robinson, not very pretty but it works.
We bought two plastic funnels (approx 4" dia) heated them up, "moulded" them into the shape of the corner of the bootbox, attached a length of plastic tubing to the end of each, long enough to protude out of the bottom corners of the boot box. Then attached inside each corner of bootbox with guess what......duck tape.
You have to be careful not to trap the tube with the boot box fixings, or it will fill up and spew over the top of the funnels. You will have to do some fine tuning but like the 2CV you will get there eventually.
When using out boot box we always cover the contents, so it tucks in down the sides, with lightweight polythene sheeting a large roll can be bought in Wilko's cheaply, we also use it to put it under the groundsheet on the tent, as you can read we err on caution rather a lot.
