I'm going to call this build done. Can't see much of the Viper but it's there! Still have to figure out a base as GW does not sell the 150mm base separately yet. There are some acrylic/MDF on eBay so I'll probably order one after the holiday.
It's going to be Evil Sunz to match the Mek on Jetbike I made.
Really happy with the Warboss conversion from the Reaper Bones model. He's magnetized and I plan on making a 40mm base for him to be on foot if I want.