It is similar and in the spirit of the original rule (which is what you want I believe), but has significant differences. Since the ISC have no Command Variants below the CC class, the SFB rule leaves things too loose at the lower end. I explained that earlier, but will post it again for expediency:
It (my rule) limits the total number of PPD's to 4 and makes sure smaller caliber fleets cannot get too many PPD's for their size and composition. The original rule would allow for 3 PPD's in a CL sized fleet and 5 in a dred sized fleet. Mine would allow for 1 and 4 respectively. The original rule would allow for 3 PPD's in a CA sized fleet. Mine would allow for 2. This allows for imaginative fleet options, doesn't restrict the use of any one ship or ship type and limits PPD deployment.
At the CC level is where they meet, allowing 3 PPD's for a fleet of three.
I believe this rule with a lowering of average TBPV's (averaging 425 - 475ish) will make it more challenging for the ISC and more fair for everyone else.