those 5 gallon buckets work awesome, same set up,, with the air gap and the res below,,, the only thing that causes people to move up from buckets is the tiny res ,, my plants can drink up to 2 gallons per day ,, so you will be filling a bucket sip a few times a day when they start doing that,, something to consider,,, have you seen the sip thread here is a link,, lots of DIY cheap builds using storage tubs and such,,, my current sip has a 4 gallon res,, i think Robs has a 10 gallon,,
https://www.rollitup.org/t/sip-thread-sub-irrigated-planter.904886/