this whole project is wonky. you haven't given enough info about it.
1. 8x8
sign. is this
sign supposed to be opaque or is it supposed to be translucent backlit illuminated
sign?
2. if solid then ok lay down red then an opaque yellow on top.
3. if translucent then do what jill said. knock out the red letters then yellow on top with 1/8 overlap. using translucent vinyl. if its translucent and your doing two 4x8 then your going to have an ugly vertical seam in the middle. also how will it be supported in the middle. how will light not shine through that middle seam. also if it is translucent you should
NOT be using acrylic. you should use
LEXAN and an 8x8 sheet if available. you will still have a vertical vinyl seam.