I'd say 12-14" overall is optimal length.
anything less and you threaten your sound signature, efficiency and consistency on making sure you can get the same speed and range like you would with a "normal" barrel.
Besides, most brands that make short barrels usually have short backs, which makes the short barrel complete crap.
I mean, you should try it out and see if it's your thing, but take the time to research.
Something like a Freak back with a stubby tip (a la WhiteWolf Airsmithing products... or from another brand... idk what there is available...) would allow you to be cost friendly as you can also grab a regular full length freak tip and you can save $10-$40 on your overall shtick and carry fewer pieces of equipment with you. I think you can do the same thing with the DYE UL barrels as well. A small bore version of those would work out pretty well as well.
If you rock a freak, avoid the aluminum inserts and check out the Empire Aluminum inserts or the SP/GOG Stainless Steel and third party Brass inserts.
You'll get the most out of the barrel that way.