I have done ra-4 in ciba tanks in the past. They need a plastic disc in the bottom to complete the light trap. Make sure that your rig has one. Pre warm the tube with hot water before the developer goes in; the develoiper volume is so small it is not enough to keep the activity up. Fortunately RA4 is mostly a develop to completion process.
I seem to recall that the ciba internal cup has a capacity of about 300mL , so that may be a bit less than the volume that Kodak etc recommends as a pre wet when working in tubes.
Any number of 70's colur printing books will discuss the details of printing colur with daylight tubes.
Have a ready supply of drying means. I used worn out tea towels that were too ravelled looking to dare hang in the kitchen and dry dished with any more. You must rinse the tube by washing at least a bit by rinsing the print in the tube. Get all of the blix out so it does not get carried over into the next run of developer, or wierdness will ensue on that print.
I used to semi-repensih with the dev and blix. The prints onlyy needed about 50mL per print, but I found that more solution would help covering the print evenly. So I would just add 50Ml of fresh developer solution to a cup that also contained the used dev. Same proceedure for the blix. Pour off the used quantity to leave only 100mL used to 50ml fresh. The first print of a session used 100mL fresh to get the system started.
Good luck with your efforts. I now have a roller processor for RA-4, but have kept the stable of tubes I once used for the day when the processor breaks and parts can no longer be sourced.