Hmm. I suppose we could work out "what is a follower worth in terms of SP", and then I could set a different, combined, limit.
E.g., if a follower was "worth" 10 SP, then 500 followers would be 5,000 SP. Add that to the 5,000 SP that's part of the above limit, and then an overall "10k SP limit; each follower adds another 10 SP" and you'd qualify.
Now I just need to remember this when I do the contest post! (I'm recovering from multiple concussions, and forgetfulness is one of the major symptoms.)
I really hope you remember when you do the contest post. Thanks for considering this.
I think I will, as I've repeated it several times in comments to others. :)