I own a pro’s pro dropweight machine. It is a simple machine, but has a solid construction and seems to be built for durability. It definitely isn’t the prettiest machine you can own, but it does the job. If you are looking for a budget option, it is a good choice. I cannot speak for the fixed clamps, because I use flying clamps. I tend to string from 23 to 30 lbs and when pulling, the machine never moves or bends. I have never had trouble with the gripper either.
I will guiltily admit that a tinge of smugness hits me when posts come around on the forum of people with more high end machines that have trouble with their gripper, or the mounting system. To be fair, they probably string much more than me, but my pro’s pro is nearly 15 years old, and by now has seen close to a thousand rackets.
Whatever you decide on, look around the forum for help with technique and habits. There are some very knowledgeable and experienced stringers on here.