weight is a better measure of your snake than length. Put him on some scales (no pun intended Lol) then aim to feed roughly 10-20% of your snakes weight, so if your snake is 200g the food item should be around 20-40g for example
1.0.0 normal royal 1.0.0 mojave royal 1.0.0 pastel enchi royal 0.1.0 cinnamon royal 0.1.0 pewter royal 0.1.0 genetic stripe royal 0.1.0 lesser goblin royal 0.1.0 phantom royal 0.1.0 Columbian rainbow boa 0.0.1 aru x jaya GTP 0.1.0 bredli 1.0.0 trans pecos rat snake 1.0.0 fat black cat
As long as the weight isn't going too high it won't hurt to try him.
Mine has taken two on occasion, normally just before she moves up a size. They can look interested but won't want it at all but I'm sure it won't matter with a 60p mouse lol. If he is taking 2, it may be time to move up a size.