Sounds like things are progressing along.
Make sure you keep on top of the design and engineering costs. The CAD hours can add up fast. Make sure everyone understands the scope of the effort.
Yeah, I checked in with them in relation to costs. They've indicated that there's a bit of fat in their original quote and they'll wear the changes. I believe they've spent a lot of time talking about it in the background and doing bits of design work. I think for them, it's a build that's of personal interest to them that it work, it's not something they've seen before hence want to see it done right for their personal satisfaction as well as mine.
Still, invariably I'm expecting some overrun. But will be told up front if it's going to happen.