My very first build was a GR-1SF. I did minimal finishing on it - just True Oil, only three coats on the neck and four on the body, and I actually left the neck setting until last, even after I installed the electronics. I used the plastic tubing method, and it worked very well. I've also built a Pitbull 12 string 335 - ES 12Q, and even though the wire runs in the GR are a lot longer, I found it much easier to fit everything - mainly because of the deeper body and no centre block.

I've built a few set neck kits, and I've found the two from Pitbull to have very shallow neck angles, and I ended up having to do a lot of work on the bridges to make them playable. I recommend that you temporarily fit the bridge before finishing, clamp the neck and string it with the two E strings to check the action. You may find that you need to shim the neck to get the proper angle.