What are you basing you assertion that #4 buck is marginal?
It will not penetrate enough to reliably reach the vital organs, especially through heavy clothing. I know of of no LE agency that specifies #4 buck.
#1 buck has been theoretically the best load for HD, superior to even 00. The problem has been that there has never been a #1 buck that patterned worth a damn. Until now. Federal recently introduced LE132 1B and I can think of no reason to use anything else for HD. I bought some about six weeks ago and it patterns as well as LE132 00.
Here is a report from the Firearm Tactical Institute analyzing HD ammo:
And here is a recent review of the new LE132 1B on the The Box O'Truth:
There are those that will argue that #4 buck is good enough, and there are those idiots who will even suggest that birdshot is the answer, but I will use the load that I know will give me the best odds of stopping an intruder. But, hey, as usual YMMV.