10" tanks are not a problem in residential applications and they do not require a hub and lateral. We do microbial testing in our facility regularly especially when we get old units in. We rarely see anything that would be of even the slightest concern especially of the systems are being minimally maintained. While regenerating every couple of weeks has no negative, regenerating more frequently than weekly starts to get a little to far off the efficiency charts without dealing with variable brining or other designs that simply are not worth the headaches.
How can you fit 2.5 cu. ft into a 9x48 vessel, my calculations when taking into consideration the domes, I can only get 1.58 cubic feet of resin. Properly design using industry standard freeboards, backwash rates and bed depths I am only seeing a capacity of .96 cu. (1 cu. ft is close enough).
10x54 is the most common tank size for residential applications. With a real capacity of 30,000 grains when using 6 pounds of salt per cubic foot, the math is fairly simple. 30,000/14=compensation and seasonal variability, lets assume 18 GPG. This would mean the system is rated for about 1666 gallons between regeneration. Estimated daily use for two people is about 150 gallons so this would put your regenerations out to about 11 days between. This will give you exceptional efficiency and good quality water. It will also allow for some growth in the family.
A 10x54 unit is 50% larger than the 9x48 system but typically only adds about 10% more cost. it also increases efficiency significantly.
And if any of the contributors to this board want me to do a quick Coliform/ecoli test of their softened water, please let me know. I can arrange for you to send me a sample and we will do it for no charge. It only takes about 48 hours for me to complete. I did my system about 6 months ago, 14x47 catalytic carbon and 14x47 softener so no chlorine or chloramine is getting to my softener, and my unit is sized to regenerate about every 25-30 days. I removed the KDF in my most recent design so as to be able to more closely monitor bacterial issues, KDF can mitigate this slightly so I did not want this affecting the test results, so far it is still coming back negative. I am not using my $10,000 Anatel a1000 obviously, just a simple culture testing system with an incubator.