As a way of practicing for the larger dinosaur costume, I've been making a centaur costume for Morgan, my six-year old. So far I've mostly completed the skeleton, which is made of 3/4" plastic pipe, screwed together, and the core of the horse torso, which is made from a carved stack of sofa cushion foam.
Sunday I spent most of the day at the picnic table turned workbench, working on various ways to attach the costume to Morgan. I've tried to prepare her by telling her since the beginning that it might be uncomfortable, but I couldn't find a satisfactory arrangement of straps that didn't either strangle her, or affix the horse torso too loosely to her.
In the end, I've opted for thick aluminum straps which travel up her back and then bend over her shoulders in a rigid frame. This is a nice setup since there's nothing to fasten; she just wriggles in and she's good to go. (One surprise for me was that, because of kids' proportions, it took me a few tries to build something tight enough to sit properly on her shoulders, but which she could still get her head through!
My surprise discovery is how nice it is to work with aluminum bars. The 1/8" x 3/4" flat bars are both strong and light. Self-drilling screws go through it like butter, it's easy to saw (with a hack saw), and it's flexible enough that with the right corner, I've been able to hammer or bend it into crude curves in a pinch.
The major downside is the cost. A 4' aluminum flat rod costs over $10 at Home Depot. I'm eyeing onlinemetals.com, which is MUCH cheaper ($2 for a 4' length) and seems to ship to Canada.. for around $0.08/inch.