Ah, but by my logic the FA trophy winners would have to also be the team gaining automatic promotion from the confrence making league team number 17. The Vase is only for teams step 5 (Sussex County) and below therefore not relevant to this discussion
Off the top of my head it's possible up to 16 different league clubs can play there each season
6 x Play offs
4 x Fa Cup
2 x League Cup
2 X Freight Rover Trophy
The Confrence Play off winners
And the League champs in the Charity Shield