It’s fairly simple using any vector editor. I’ll give the example using Inkscape. A quick note: There are a lot of words here, but in reality this process should literally only take about a minute to do the scaling, then however much time you take to do any manual adjustments (described below) is up to you.
First, measure your material and decide how thick you want your slots to be. Let’s assume our theoretical new material is 2mm thick. You’ll need to kerf adjust the cut line, so you need your slots to be 2mm minus some kerf adjustment, let’s assume you’ve worked all this out and you decide that your slots need to be 1.85mm. (that’s about a kerf of 0.006" It should end up snug but not a pure friction fit… you’ll have to figure out what kind of adjustment you want to use on your material, Acrylic for example, unforgiving… woods, a bit moreso.)
OK now you have your desired slot width in mind.
Open your model file.
Measure the existing slot width. It’s 3.050 mm as is.
Now select all and let’s modify the overall size. To scale it you want to multiply by the desired slot width and divide by the existing slot width. So first lock your aspect ratio and then you add “*1.85/3.050” to the width (or height) field. The entire model will resize.
Now measure your slot width to be sure it’s right and you didn’t typo anything.
Perfect. Now you have to sanity check the model. Did you size anything out of existence? See if anything looks super thin. A good way to gut check this is to set the stroke width to be about a kerf (0.007" usually works), and you can eyeball a lot of it. Look in particular at the red areas highlighted here.
Here's my thought process for this theoretical example:
The hooks on the feet are vanishingly small, you could consider modifying the path to remove them, and the tabs where the wings connect are pretty skinny, you might want to modify those to be a bit wider. Those are judgment calls, and completely up to you.
The wing filaments are about 0.7mm thick, those should be ok… almost everything else is even thicker. The antennae are going to be delicate, but they also look like they’ll hold up, just be careful.
So anyway, assuming you tested your slot width and got that right the first time, this should work fine. My bee worked on the first go.