Finally bought a 15L unit. Looking at the usual outlets it was about the best price/size. 22L and 30L units were still only 6" or 8" deep. It appears until you get to a better quality unit you don't get much over 6" of solution depth. I also realized I do not want to heat 5+ gallons of fluid to clean a part. Much bigger than what I got I will clean in a parts washer.
Update. The 15L unit has an issue with the heat side of panel. The seller on FleaBay advertised 30 day returns and free return shipping. After 7 days of back and forth...them offering $50 to take it to a repair shop, telling me to turn up the power, P=I x V, etc. after 7 days they gave me a full refund and I still have the unit. It will heat, but not properly. You set the temperature, unplug it, then plug it back in and start heat. If you adjust temperature while it's running it states the actual temperature is only 44°C. It goes silly... they finally acknowledged they know of the problem and do not care. Like my buddy from Miami I got the item delivered free!