go check this page on lv40 bandit Keith, not the quite same i Know, but it should work too cause most of his mons are still machine, if you lose too many times, then just face lv 20 bandit Keith
I battle the last 4 LDs on level 20 usually, as I do not think it is worth risking to loose rolls on them just for a 75 coin difference, if you could already be in the next round stomping the other LDs with a simple fusion deck. I think my deck could beat Kaiba 40 as well but I needed to starting hand enough for buster blader fusion to deal with Blue eyes, not worth the risk.
bandit Keith kept beating me by getting his monster up to 2000 attack points on the second turn and I had nothing in my hand to stop him but I finally got garlandolf, king of destruction from the shop and got lucky enough to start my hand of with a 1700 atk point monster ,de-spell,block attack,and him and was able to defeat him without a problem.