Rubberbanding still a issue?
My server has around 80+ players,   rubberbanding is really bad.

Worked fine just after wipe but today it's been really bad,  the server i'm using is high spec we upgraded thinking that was the issue. 
what version are you on, and what is your fps.limit set to

fps.limit: "256"

So basically today I had  v1.3.8 installed, rubberbanding kicked in so I upgraded to v1.3.9 

just before it displayed this message in the console

(20:09:44) | [Raidable Bases] Grid initialization completed in 52 seconds and 326 milliseconds on a 4500 size map. 9479 locations are on the grid.  

the rubberbanding was really bad but the bases failed to spawn,  I restarted the plugin again and same thing, rubberbanding but failed to spawn the bases so I  reinstalled v1.3.8 and the rubberbanding came after 30 minutes.

Is it possible to specify a spawn point location rather than Grid initialization?

yes. you can set custom spawn files in each event category to bypass the grid.

also, fps.limit should be 60. having it so high will absolutely cause lag as the majority of the plugin works off of frames per second.
Setting to 60 will definitly help with lag.