The times did not agree with the temperature they were cooking at. This has been my worry about reverse flow
Its not like the reverse flow is that much different than an off set smoker, cooking temps and techniques should be about the same. Its just that the reverse flow fixes many of the problems associated with the traditional off set smoker and wraps it up in a very nice package.
Think of the of the reverse flow plate as one large tuning plate, except that the plate does not need to be adjusted when doing different size or quantities of meat, nor is it going to bounce around when transporting the smoker and have to be reset upon arrival at cook site. Being fixed, it will always be consistent, making it easier to produce consistent product. When the reverse flow plate is fabricated as a drain pan as well, with plumbed in drain pipe, it eliminated the need to place aluminum drain pans inside the smoker to catch the grease, also eliminating the need to empty those drain pans. This keep the smoker and the cook place cleaner and more organized. The reverse flow is basically self cleaning, with all dripping flowing into a conveniently placed bucket that can be emptied with no effect on whats going on in the cooking chamber. And the reverse flow smoker by design is more efficient, due to the heated air stays inside the chamber longer, allowing more heat transfer. Temperature control is usually better in a reverse flow as well.
But other than that, its still an off set smoker, and all the talk about how food taste different or one cooks faster or slower , really is silly.
So my answer to the question about a "hybrid" is Why? Why would you want to build something that only had some of the improvements listed above and not all?
How far away should the reverse flow plate be from the cook grate
Honestly, it really does not need that much room, its not like you need to get smoke up under the meat. And as long as its built right and does not have any hot spots, a few inches is all that's necessary. On a pit the size your talking about, I'd probably go 5 or 6 inches from the highest point of the plate ( if it will still give you proper air flow under the plate)
and is it better to just do a half moon cut out for the FB or cut the corner out like the Meadow Creek cooker has in the Photo you posted
When doing a tank build that has rounded ends, I like to notch it out. But with flat ends just but it up with a half moon. If you notch it, it will take away from your cooking area and give you a hot spot on that end.