Norm Sanders
Script Wrangler
Don't worry about length at this point, just write it & see that it's strong. If it's WAY too long (i.e. 15 pages+), then look to see where you can cut out some fat without hurting the story/characters too much.
Even if after it's shot, if you're at 7-8 minutes, you'd be amazed how much you can clean/tighten something up in post to get it to the required max.
Even if after it's shot, if you're at 7-8 minutes, you'd be amazed how much you can clean/tighten something up in post to get it to the required max.