That was heartbreaking ... I just wrote a 10page response and it disappeared. Not doign it again. Here's the short story.
That's pretty short for a hill bow if you ahve a 28" draw, what's your draw length?
What tools do you have?
Is this you first bow?
I think a backed bow is going to be harder than just a simple board bow. I'd buy a couple good oak or hickory baords and build a couple pyramid bows to get the hang of tillering first. There are numberous build alongs on here and the web in general.
Your hill bow would probably need to be bamboo or hickory backed ipe or osage. I'd probably make bamboo baked ipe personally ... just preference though.
You don't need the riser,
http://poorfolkbows.com/ipe1.htm Sam harper talks more about it here. Same applies for simple board bows. You wanna use solution number three as Sam does.
Hopefully others will chime in.