Some confusion here, big difference between sanding and grinding. I've tried a number of different models of these devices, and while they're great for sanding they suck for grinding. I can do better with a vac hand held, because of the necessary angle of attack of a grinder, as someone mentioned previously. Good tenting is the best answer. Some of the shops I've worked at have gone to great lengths, from dedicated grinder booths to some rube goldberg devices we built ourselves. For marina work in very picky high end local marina's, we built a plexi box with rubber gloves built in and a vacuum outtake with foam seals
on the bottom edges. Think upside down plexi aquarium with heavy duty gloves like you see in bio labs in movies and a vac outtake. No dust at all, you move it around on the work surface and vac as you go. But for me, the harsh truth is that no matter what system you use, enough itch dust will escape to make your life miserable and bring the EPA down on you unless you tent well and suit up. So why not just skip the devices that slow you down and affect the quality of your work and just tent well, suit up, bang it out, and clean up very thoroughly? I find it goes much quicker this way. Our shop threw away all such devices for grinding (except the box, which really just shows a good faith effort to the nitpickers) years ago. Now if we were talking peelers or turboshears here, it would be a different story, we have awesome vacs we built for those. I should post some pics of me suited up and under a major keel
grind in the pouring rain, lying in a puddle of water
2" deep with foot deep fiberglass
dust turning into mud all over me. Done it for years. No vac can keep up with that kind of major grind. You should see what happens when I fire up the shears...