YES, I made my own "Mast Mate" type ladder system and have used it a number of times to climb my mast
solo. I used 100' or so of quality sailing line, tied alternating loops every foot or so (so each step is approx. 2'). I put about 6" of PVC pipe on each loop, this allows comfortable footing without the rope loop cutting into your foot. I also tied in a mast
track lug at every other loop, allowing the ladder to be hoisted up the mast
with the main halyard
and remain very stable in the track. Total cost was ~$50 (as opposed to $300 for a mast mate).
I have a simple climbing harness I use when climbing my ladder. On the harness are two heavy lines about 4' long with a carabiner on the end. As I climb the ladder, I always make sure at least one of those carabiners is clipped in somewhere independent of the ladder line. One trick for doing this is to lower the jib
halyard, tie loops in the line every 4' or so, and re-hoist it. Then you have an independent line to continuosly clip into as you climb your rope ladder.
Make sense? Kinda hard to explain in words, but it works real slick, and in my opinion using the always-clipped-in method it's fairly safe.