Banjo uke build

I am making a banjo uke out of a mainland ukes baritone neck kit and a 12" pre-tensioned drum head. Looks like I need to add a spacer of an inch or two between the neck and drum head. Looking for suggestions on the best ways to add the spacer and also attach the neck...do I need a dowel or rod in the head or can I just bolt the neck on? Looking for ideas, I am planning to play clawhammer style on this uke like I do on my 5 string banjos. I have put a couple of banjos together and have some woodworking skills and tools. I did find a web site with pictures of something similar to this (but not baritone scale) and they just bolted the neck on. http://ukuleleguide.com/banjo-ukes.html. Not expecting this to be a prize winner or anything as I like a rustic look (think hand made mountain banjo). Thanks, WC

See if this helps.....

Blessings,

Kevin