Since your friend wants to shoot no more than 20 yards, putting a jake decoy at 25 yards will bring a tom in right at 20 yards. Normally, a tom will come strutting in and will face the jake decoy before he initiates a fight with decoy. When I hunt with my bow, I'll position jake decoy at 20 yards facing me and as gobbler comes in he'll circle decoy in a strutting position then will face decoy before he spurs the jake.