If you can't fit your hand behind there by route of going through that open hatch space, I'd say your best bet might be to drill the bolts out, you can likely catch whatever's behind (like the bolt nut) when if falls into that open space in that compartment, assuming there's any amount of access between them.
Instead of using sheetrock anchors checkout beauclips, they're cheaper, way easier to install, meant for this application, and make it far easier to maintain your upholstery down the line, way more rigid than something like Velcro too.
Using my mother in laws Janome 6600. My husband and her are sewing the seats. Great bonding time for them! I'm just along for the ride. I've always wanted a ski boat. My husband has always said no. When this project boat came up for sale we compromised and got a ski boat.
I believe that machine has a built in dual feed attachment. That's basically a "Walking Foot" feature. Do you know if they are using that? If not they should and also be using the Longest stitch possible. When sewing vinyl the fewer holes punched in it the better. Also I think they can get a #19 needle for it and if so they can use #69 Marine Thread which would be ideal. PM me with your phone# and I'll be happy to talk with you about any questions you might have about the process.
Woodonglass. Thanks! My mother in law has thankfully sewn with vinyl many times. Her machine is quite fancy. Hit a button and it automatically reverses and cuts the thread.
