Well, I won't get into a debate about if you should or shouldn't be using them. But, rule of thumb for many many years when it comes to stacking test with something like deca, is that the deca should be half the dose of the test.
In other words, if you are running 800mg of test, you want to be running 400mg of deca.
And because of how long deca lingers in your system, you may want to think about stopping deca all together 3 weeks before your cycle is over. You will recover much better.
Also, you can switch from enan to prop in those last 3 weeks as well, that will also be very helpful. Good luck.