Raising an Eresus walckenaeri sling

Hello All

I have gotten a tiny Eresus walckenaeri (Velvet Spider) sling recently and I love it, but I am terrified of how tiny it is. It is about the same size as the fruit flies that it eats (about 3-4 millimeters). So far I feed it a few fruit flies every other day and while I rarely see it eat them, I find an increasing number of "leftovers" around its little web hide, so I think that it is doing well. It almost never comes out though. Has anyone else raised a Velvet Spider from a tiny sling before? When do they grow to a size where I might actually be able to see it without needing to zoom in with my phone camera? Are there any other tricks that I can use to check on it without disturbing its nest?