Quote: (Originally Posted by
decoweenie)

I sold the MK-15 years ago, but I also had the Inconel spheres as well. They both fit in same space.
Phi's Mk15 had floating 1st stages, whereas the Mk15.5 has mounted and hard plumbed 1st stages. The pillar valve has to be just right for the spheres to fit in. Unless someone has already tried the 15.5 with composites (maybe one of the HK boys?), you'll just have to suck it and see.
Cheers,
Jason.