Hi @NewGuy ,
I did not cut plastic yet on the Maslow. Yet, let me share what I have seen and red about it with the context of MalsowCNC.
Now grooving is not exactly cutting, and the difference is about depth. The lighter a cut, the lower the forces and the heat…
Do you have some information about the EVA or PE foam product? A product description, ideally a product specification from a manufacturer might give you important details like the melting point temperature or the health and safety advices to prevent problems.
One thing is for sure: plastics are often described by their core matrix (poly ethylene , and poly ethylene vinyl acetate here?) and almost never list the set of additives, which are important because they set most plastic properties.
Basic Poly Ethylene typically has low meting temperatures. But some products are made with insdutrial manufacturing process in mind. @aluminumwelder here points out some material and distributor
Now the Maslow is based on a router of your choice. Some Maslownians also opt for a spindle, which offer advantages on speed and noise.
Typically, a router will spin fast: too fast for plastics (heat will build-up and plastic softens) which may lead to poor quality edges. That was pointed out here with the idea to create jigs on maslow then cut plastic parts with the jig.
One might seek a balance by accelerating router movement speed, but note that the standard MaslowCNC will produce 800mm/min at best in x/y directions. And you might look for a fast Z axis mod to avoid idling too long while the router is diving in.
The router bit shape (upccut) would be important according to @aluminumwelder here
That is why you might also seek for a slow router / spindle, speed, and a single flute cuter. To that extent, there exists speed controlled router but the slow speed setting might be too fast still (typ 10 000 rpm). Some improved additionnal speed control migh provide stable speed down to 5000 rpm. Is that slow enough? Well here are:
And @mrfugu reports several point for
- Machining guide suggestions
- Safety guidelines
- And a page to share materials findings
Over all you need to try or find someone who did. 
Anyone?
Hope this helps.