Best Insulation Scheme for a Finished Attic

Hello, I am re-finishing an attic in an older home in Ohio. I have removed all of the existing walls and insulation. I am down to rafters and I am now ready to start the project. I would like to insulate the attic the best way possible as prior to the remodeling it used to get pretty hot up there in the summer. I have 6" trusses with about 5 1/2" available space between the roof sheathing and the living space for insulation. The house has 2 gable vents but does not have soffit vents, but I am going to put them in. I was going to put those styro rafter vents starting at the soffit vents through the section of the roof that is the angled ceiling of the finished space, but they are a whooping 1 1/4" thick which really reduces my space for insulation. While wondering in the home improvement store I came across reflectix radiant insulation. My idea now is put the styro rafter vents at the soffit vents to keep the blow in insulation on the floor of the attic from blocking the air flow. I was then going to staple relflectix between rafters starting at the bottom of the section that is the angled ceiling, up over the top flat area and then down the other section of truss that is the angled cieling on the other side. I plan on doing this leaving a gap of 3/4" between the reflectix and the roof sheathing in the sections that is the angled cieling. I am then going to shim out the rafters with 2x2s and add 5 1/2" thick high density unfaced R-21 insulation between the reflectix and the inside edge of the living space. I plan to finish it all off with a poly vapor barrier. This should give me about R-30 for the attic space. Does this sound like a good setup? Is it ok to put fiberglass under radiant insulation such as reflectix in roof trusses? Am I going to have any moisture problems? I would think that reflectix is a 100% vapor barrier so it sounds like I'll have a double vapor barrier with this setup? Is that a problem? I am thinking this is ok because those styro rafter vents would also act as a vapor barrier, no?
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