>1. Can I use straping for the top bars.
I have no idea what straping is.
> They are not a 1/2 inch thick, but I was planning on cutting them down to 1 1/4 as well as 1 3/8 inches for the brood and supplies bars respectivly. I was going to make the between 15 and 17 inches long (I have seen both messurments here) I want to see how much this changes the slope of the sides.
How thick are they? I have never gone less than 3/8" thick and that was in a hive made to take Langstroth frames as well as bars. The slope of the sides will be whatever you decide to make it. You cah have whatever width you want, or no slope in the sides.
>2. How deep does the grove in the center of the bar have to be?
I have no grooves in the center of my bars. I put triangular comb guides on. You can make these or buy Chamfer molding.
>3. What is the difference between the end entrance and the entrance on the center of the side.
Drilling holes and not drilling holes. Mine are on the end and I drill no holes. The entrance is just the gap at the front. Putting them on the side is difficult as you will tend to get a gap at one end anyway, so then you'll have more entrances, which is not necessarily a convenient thing for you or the bees.
> Is there a difference between the long opening and a hole drilled in the side?
You'll end up with the long opening anyway when the wood shrinks and/or expands and you have to pull a bar out...