I have used both of Martin Creeks Storage racks. The KSR-1000 is very easy to use, the neoprene covers keep the kayak from touching the metal. The J-Rack works great in my garage where space is important.
Each time I have ordered a rack from Martin Creek it comes super fast. I have ordered from both the web site and over the phone. The Owners are the ones you talk to when calling and have always been super helpful when deciding which rack is be suited for my needs. I will be ordering again soon with another kayak on the way this spring!
The neoprene sleeves slide around and can easily expose your boat to direct contact with the rack bars. The bars themselves are soft and fairly easily bent or twisted.
You must be careful of the rack if you have a plastic boat and handle it yourself. Ours are about 60 pounds and unless you are very careful of the rack, I wouldn't go with anything heavier.