Great to hear you got your k4.6ho rebuilt. Its an ok engine for your HF and should last along time.
I used similar breakin on my 4.6 and os28 and both engines still strong. I ran them a little rich for 3 to 4 minutes up to a good temp then let them cool at bdc ( i had cooler air from my car aircon blowing on them to speed up the cool down process). I did this for about 10 times while slightly leaning out the hs needle. After this i ran the 4.6 fairly hard and all ok. I took a little longer with the os. For engines with a very tight pinch you do need to put a gallon or 2 through to ensure a good breakin.
You need to have the servo saver very tight to get decent steering from the hf, but you do risk stripping the servo horn, or as i did cracking the servo case(after a heavy hit). The servo saver does loosen by itself so keep checking it or even a dash of loctite.
Remember loctite alot of your screws or they will vibrate loose. Also keep an eye on the mid range needle as it has a tendency to loosen and fall out.
Go hard and let us know how it goes.
Craig.