48K GPG unit is overkill. You need a 40K at most and may be okay with a 32K unit, depending on your actual water usage. Take a look at
www.hvacandwater.com/ws_main.html for the calculation breakdown and a lot of great info on water softeners in general.
You are forgetting about the constant SFR (service flow rating), and looking at your web site you do not mention it but very vaguely. Exceed the constant SFR gpm and the softener is undersized and will allow hard water breakthrough.
A "32K", actually a 1.0 cuft, has a 9 gpm constant SFR; a 1.5 cuft has 12 gpm. A 2.5 bath house with 2 people there can exceed 9 gpm. It depends on how many fixtures they run at once, or if they have any body sprays or 2 person showers or a large jetted tub etc..
I'm not sure if you know that you can adjust the salt dose up and down on all control valves. That increases/decreases the K of capacity and salt efficiency. Or that all softeners are sized by cuft volume of resin. Sizing for the peak demand water flow through the softener is critical and that dictates the cuft volume of resin required. Then you adjust the salt dose to get the required volume of capacity needed for the regeneration cycle you want to use; on average and depending on the iron content, once every 8 days is best.
BTW, Fleck made all Culligan valves for like 50+ years and Culligan still uses the same (Fleck) piston, seal and spacer design of all Fleck (and Clack) valves. Fleck has made the control valves for more national softener brand companies than any other control valve manufacturer. And for the longest time frame. Fleck, Autotrol, Erie, Clack, the four control valve manufacturers do not make softeners or filters, they only make the control valves used on them.
You mention Rainsoft on your site.... they use a Fleck valve modified to their design which makes it proprietary. RS is famous for undersizing softeners.
Ecowater makes all the big box store brands; GE, Mortonsalt, North Star, Whirlpool, Kenmore and possibly walmart.com. They do not sell their control valves separately as Fleck etc. do. All their valve parts are interchangeable as are their valves and tanks. They are not very good quality IMO and have the shortest of all valves. All are proprietary meaning you can't get service or parts from anyone but their dealers etc., that includes Culligan, Kinetico, Rainsoft and most other national branded softeners, even if the valve was made by Fleck or the others.
All Kinetico softeners take the tank being regenerated off line during a regeneration. Most only allow water through one tank at a time during service. That applies to all twin tank control valves, including Fleck, which sells many more than Kinetico.
Also, control valves barely use any electricity, so why do you say on your site that larger softeners use more electricity than smaller ones?