I haven't had any problems with locks but I only use them when car suspended for a while, I use 4 x 4 for trucks and SUV's, I couldn't justify the money for adapter kit. Looks pretty easy if one wanted to build a set.
I just joined this forum but have paged through from time to time, I bought a Atlas kwikbay 7000 2 years ago and have had probably 75 cars and trucks on it. I love it and for short ceilings and portability factor its a awesome piece of equipment