You say 8 points and you say one single R8216. This infers that all four ports on the R8216 would have two points each.
I know I am now stating the obvious below, but just on the off-chance that you are thinking differently.
If you do connect the 8 points in that way, you can only operate the 8 points in pairs, this infers that your layout design has four pairs of points configured in 'cross-overs' with no sidings. When you connect a pair of points to the same R8216 port you have NO individual control of each point of the pair. If you haven't got four cross-overs and want control of individual points, then you will need a second Accessory Decoder. Note that the R8216 is obsolete and replaced by the R8247.