Conditional Formatting Add 8 hours

Hello world,
I am attempting to use conditional formatting to shade cells depending on completion times. Here is my setup and as always thank you very much for any and all help.

F2 = Start Time
R2 = Completion Time

Here's my formula for red.
=$R2<($F2+8/24)

Rules
Less than 8 hours from start to complete green
exact or 1 hour over yellow
greater than 1 hour over red

I believe the issue I am running into is, since all of the times are overnight, when the time rolls past midnight the formula automatically assumes that it is way over or under the set formulas. Is there a way to do this without adding new columns? I've attached my testing spreadsheet to here as well.