Only problem I've ever run into is clearance getting the car up...slow and easy. Would never even try plastic ramps. May be perfectly safe, but I like my ramps like I like my cars....steel. I'll use ramps over stands unless it's suspension related, of course, as I find the stands always end up in my way somewhere down the line. Ramps go under the tires. If the ramp is in the way, the tire is usually in way too, it's time to rethink the process. Personally, I think ramps are safer than stands; less likely to tip or get off balance if you're really cranking on something. May be obvious, but I learned several years ago to NEVER crawl under from the side. Long story short, crawled under an '84 Cutlass from rear, car rolled off ramps (long story part), thankfully I wasn't from side. Thought REALLY skinny and ended up with not much more than a nice scar over my shoulder from the differential. Now, what I was doing, would probably have knocked the sucker off stands as well, but then I would have had a different situation on my hands. I go under from the front even if I need to check out the tranny or the driveshaft now. Don't think I've ever seen something so scary as a 3300 pound car go into motion with me under it. :horror: