Adrian, check on unblinkingeye.org about semistand. Anyhow, I would recommend to give any stand or semistand development a good thorough agitation to start with, i.e. more like 30 sec instead of 10 sec in the beginning.
About volumes, I think 75ml/sheet is recommended at 1:1:100. If you dilute more, you have to see to using at least .75ml of part A for each sheet.
If you still want to use the CombiPlan, it should be fine as development times are quite long. (I take it you will dilute the dev. at e.g. 1:1:200 or so, for which times will come to 20-30 minutes with semi-stand.) In that case, the time it takes to fill/drain it doesn't affect theresults at all. Also check a recent thread on BTZS tubes which discuss stopping and fixing in normal light.
//Björn