EVA foam thickness and costume size

[Fost9508]

Probably my first post, so not sure if this is the right sport for this question. I have worked with EVA foam to make a Rocketeer helmet so have some experience making templates, cutting, shaping, gluing and painting, but on a smaller scale. I am making a costume that involves a shark. The shark portion is going to be around 52" long and roughly 16" inches in diameter. So this will be the largest thing I have made with EVA foam. I was going to buy a role of diamond plate foam from pep boys, but it looks like it is about 1/4" thick. Have others had experience making a foam costume of this size using ~ 1/4" thick foam? I was thinking I could add some foam structural members inside to provide some rigidity. Otherwise I was going to use 1/2"

Here is a scale model of the shape I am looking to make with the foam.

 

[Zinger]

When Evil Ted had to make a large costume like that, he used 1 1/2" thick foam rubber. From the video, it looks solid enough to hold its shape without any reinforcement. The construction technique was basically the same as using EVA.