What constrains are that? Anyway, latest SP for 8.0.x is SP3 and there it says clearly (see release notes) that 8.0.x will not support 5.5 - 8.1 will. Now, back to DD - I assume you use some DDOS 5.2.x? Matrix for DDOS and NW (based on Boost) says that DDOS will support previous (n-1), current (n) and future (n+1) releases when it comes to compatibility. So, if you run 5.2.x, you should be fine with NW 7.6.x, NW8.0.x and NW 8.1.x.