All looks good. Open door is fine for the first couple of birds and if you send everything each week but you are better off having a trapping system or a sputnik etc for the birds to trap into and then be confined to the loft.
The open front will help with your pfl but i would make an overhang at the front of the loft which will not effect air flow but will keep the majority of the rain out.
sec doesn't have to be a member but if they aren't and there is any dispute the club would not get assistance from the union or be able to deal with them as non members.
Everybody i know of dreams about winning a national etc who do you know who dream about winning a sprint?
Why are nationals flown from the distance and not 100m? Anybody can win/get birds home from 100m but how many get them from 500m +?
went up to Aberystwyth this morning and it was as clear as a bell until we nearly reached Lampeter and it closed right in, after a couple of miles it was clear again so there have been some dodgy areas around.