Replying to Sanding bases

I have had my skis (08' k2 silencers, red target graphic) since I started skiing ~4 years ago. They have been my only pair, and they have received some abuse both intentional and unintentional. Skiing over parking lots, salt and sand, plenty of rails, grass, some pavement. At this point, any shop I take the skis to refuses the base grind because they are so beat down. Last base grind I had was before last season when my bindings were re-mounted and the tech messed up and pushed the screws through the bases somewhat.

So I ask this question, could I do my own base grind with a belt sander? They are so slow and hold no wax so anything would be an improvement. Damaging the edges isn't a concern because underfoot they are so worn that they are completely rounded. I can't afford new skis yet since I am a full time college student but I need a little extra speed.