Water softener sizing for changing water usage

[SoftenerNewbie]

Been reading articles online for past few days but still can't makeup my mind about which size softener to get.

Water hardness: 300ppm = 17.5 gpg
Min people in house: 7 people
Guests: Every 2 months or so we get 2-3 guests that stay 2-3 weeks.

The valve is Up-flow regeneration metered Runxin (chinese). Would like to use the salt efficiently 8lb/cu.ft should be good enough. The installer said that 13x54 vessel with 2.5 cu.ft Purolite C100E resin is good size for my needs.

Does that sound good? I was thinking of going with 16x65 (can't find 14x65 vessel locally) considering with low salt regeneration, the softening capacity is reduced as well. OTOH, I was reading that for Upflow regeneration, the resin bed depth should be min 3'3", would 4 cu.ft resin in 16x65 vessel be enough to achieve that height? Also read somewhere that with gravel bed, we don't have to worry about resin bed depth and channeling issues during up-flow regeneration?

 

[Reach4]

16x65 would normally us 4.0 cu. ft. of resin, or 4.5.

Upflow brining needs gravel plus a low-enough injector flow rate. I don't have numbers for you, and I don't know your valve.

 

[Sponsor]

 

[SoftenerNewbie]

Valve: https://www.run-xin.com/en/content7_372.htm
Manual: https://www.run-xin.com/upload/20190627/153734581337.pdf

My main concerns are:
1. Is 13x54 with 2.5cuft resin enough for 7 person household, while being set for low salt usage?
2. The injector they sent me is Yellow/orange looking. In their book yellow injector (6303 = 0.75 gpm) and yellow injector with green throat is highest-flow injector but my injector does not have green anything on it, its pure dark yellow looking.

Also, the included BLFC are DLFC parts are the ones both listed under DLFC in their manual. Parts 8468062 (6.6 gpm) and 8468063 (8.1 gpm)