Plugging 12 x 12" X 4" Concrete Hole. Advice Needed

I am patching in a 12 " by 12" by 4" 3-4" thick area that I had to crack concrete out of to replace a shower drain assembly. I have drilled the perimeter with 1/8" holes and sunk 2 1/2" masonary nails (two on each side total 8) to act as keys and was going to pour a fast curing cement and sand mixture. The manufacturer (rapidset) has a concrete mixture but said for my application no aggregate would actually be stronger. I have heard about sinking 3/8" rebar sunk 3" with Simpson glue. Also, it has been suggested that I might use concrete with an aggregate mixture. But rapidset seemed to think as I that masonary nails would also be a good idea. I also think with the area I am filling what I am planning seems more than adequate. I cannot even remove the nails with vice grips now they are in so tight! Any advice from people who actually do this. Are the varying opinions I am getting correct, or is rapidset correct. Thanks.
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Michael "anal" SloBrain anally wrote the same anal post he anally wrote last week:

It's a simple little task, anal SloBrain. Go back and read the previous replies to your previous post and quit being so anal about the whole anal thing. Unlesss you plan on building an anal frikkin high rise on it, just anally fill it with mortar for krist's sake.
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