Some time ago, I reported on fitting ceramic stay alive capacitors to my little class 02 shunter. Subsequently I found out about the performance drop-off in ceramic capacitors near their rated voltage, and that means their performance for stay alive isn't as good as one might hope.
So, mindful of that, I've replaced the stay alive unit in the 02. Out with the ceramics, and replaced with four 220uF, 16v rated Tantalums. Those are fitted in both cab-sides, two capacitors to each side, so the cab-light in the loco had to go (but it didn't look particularly good, so its main function had been to test whether the stay-alive was working !).
Net result, about 1/4 of a wheel turn without power at moderate speeds, far more than what's needed to get over a spec of dirt. And, that's made me think about the DY1 shunter I built over a dozen years ago, and about finding space in the cab for capacitors in that loco.