I used the original holes that were on the RL01 and think maybe one lined up with the rail that I used. Did end up drilling maybe one new hole in the slide rail center to align with existing hole on RL, maybe a second but cretin there are no more than three screws on the rail on each side to hold onto the drive. Also the screws were a cretin length and fit into a sealed threaded receiver to keep the seal of the drive. Looking at other system always appears that the drives are up top to spare the back of the operator in pulling out and loading the drives but I put mine on the bottom because of the whole if you pull it out the rack may tip over thing. Also by installing on the bottom you can use books to stack underneath and get the rack placement right. A signal with blank rack panel will fit between the RL and the bottom memory unit but did not put one in because clearances would have been tight in pulling out the drive but being that I only have two RL disk packs and one is bad almost never pull out the drive anyway. I have a couple of the five foot full size black Dec racks here at work with other stuff in them and if I ever get a unibus system will pull one of them for that being the original Dec racks have a sideways back rail to attach to the cases and the attaching points for the front outriggers. I did not put any outriggers on the little rack for the 11/23 but being that the drive is in the bottom it has no issues when I pull it out of the rack, do not know what would happen if it were on the top. Also another thing I did before wasting several days building up slide stuff for this was I had a six foot roll around rack with the system, two drives and a RX drive all in one rack and I just used the slide brackets that APC makes for their rack mount UPS system. They are way thin and can support huge heavy UPS systems and the RL drives or just about anything else can sit on them in a rack and slide in and out. The hairy thing was with a RL drive the CG shifts to outside the rack when you slide it out enough to open the drive so if you're not using slide rails attached to the drive things get real ugly fast if you try to change the pack.
Another thing to keep in mind is that if you're racking up a RX drive the rails have to be way long so you can pull the entire assembly out of the rack but still be attached so you can remove the bottom plates and replace the drive belts, maybe that’s why they come with long cables?
Got pictures of what you're racking?