I think that chestplate sizing is absolutely perfect!
Shame about the blasters. Were you able to solve the riddle of why the paint didn't work?
E/M - scale looks right.
Kandosii Tor is spot on that EVA skills translate to Sintra. Check out Flo Brin's thread about making this style chest plate from Sintra, using a foam template. Very good photos of the process.
Here's her full WIP
Thank you for the feedback and the resources! The threads were very helpful to read through and I feel a lot better about sizing the rest of my kit knowing I'm on the right track with the chest plate.
Update:I wasn't able to really figure out what went wrong with the blasters, but I'm leaning strongly towards paint incompatibility. Good news, I was able to salvage both blasters.
2 piece blaster (bottom blaster in the above picture):This is the one I hit with the red first. The red never fully cured. I was able to scrape and sand it off.
Following a large portion of the advice I received, I ended up buying Montana primer and Montana gold paints. I put the primer over the weathered steel in the areas I wanted to paint red/brown. I then layered red/brown Montana paint over that. It did adhere, but not great. When I pulled the painters tape off, the Montana paint wanted to go with it.
I gently pushed the paint back down and gave it a couple more days to dry. It seems to have adhered better as it cured. It only chips off when you drop the blaster on a non-carpeted floor. I went ahead and weathered the end result. All it needs now is a top clear coat (staying with Montana). Depending on how durable it feels after that, I'll decide if this one is wall art or part of my kit.
12 piece print (top blaster in the picture):This one already had the rustoleum weathered steel on it when I sprayed the red on the 2 piece blaster and realized we had a problem.
I gave the 12 piece several more days to cure (in case the issue was gas evaporating form the still curing steel layer), washed it windex (for surface contaminants), handled it exclusively with new disposable gloves (again for surface contaminants), sprayed a layer of rustoleum matte clear sealant, and then sprayed the red. It had the same issue as the first blaster.
At this point, i had just taken the tape off of the 2 piece blaster and wasn't sure anything would stick on top of the weathered steel, so I stripped this blaster back to plastic using orange wipes.
With everything except the PLA and the bondo gone, I started over on my paint layers. I had success with the rustoleum primer and filler (followed by a light sanding) and then the montana paints (primer, matte silver, shock brown, and brick). I then weathered using an acrylic wash and will hit it with the Montana clear coat tomorrow as well. The paint feels very solidly attached to the blaster.
Helmet:After watching several Youtube videos on custom painting black series helmets, I took the plunge. The Bo Katan helmet is not put together the same as the Boba Fett style helmets, but the range finder ear cover pops off the same way. Once that was off, I took out every screw I could find. If it exposed electronics, I put the screws back...


I then started sanding. The only areas that I found really needed sanding to even them out were a parting line on the back third of the dome and some spots on the forehead where the edge of the white "mask" paint was raised. I didn't sand it back to raw plastic, but I hit everything with 120, 220, and 320 grit sandpaper. Next was rustoleum primer and filler. I did this based on the number of people I saw have success without any sanding and the fact that I did didn't want to make flat spots.

That got sanded with 220 and 320 after it dried.

Next up was Montana primer (2-3 dusted on layers, with 320 and 600 grit sanding in between as needed).

Then 3-4 coats of Montana Gold matte silver. I did sand this with 600 grit between coats 3 and 4. It has a somewhat gritty texture if I don't.

Tomorrow I'll put on the toothpaste and start laying down colors.