I would caution against adding it before the 1 year mark for the following reasons.
1) although there are a few hardy SPS, I'm assuming when most people talk about SPS, their goal is to eventually get acropora. So, generally speaking, SPS needs a lot of stability to flourish. Maintaining the perfect parameters is only one side of the coin. The other half are all the environmental conditions we cannot measure and control - bacteria, microfauna, DOC, pods, and how they weaving a intricate web of cause and effects. This half we cannot hope to control. Dosing bacteria and pods is going to be hit or miss bc we cannot measure how they interact with one another si its all guesswork. This intricate web is just as important as maintaining water chemistry (no3. Po4. Alk, ca, mg, ph, etc..) and this web is only achieved in the tanks natural maturation process, and unfortunately, the only thing that get you there is time.
2) With out a mature tank, its not impossible to keep SPS, but it will be a lot harder. Inevitably, due to what I mentioned above, your tank will go thru cycles, SPS will be the first to go from these fluctuation.
3) in these forums you have take all the "I added everything right away and everything is fine!" response with a grain of salt bc there is going to be a lot of confirmation bias bias there - people are a lot more likely to respond to you when they have a good outcome than if they had a bad one. People are a lot less likely to respond to you if they added SPS right away and everything died. In fact a good % of those people will also give up the hobby altogether and not even show up in these forums. Even the ones that had positive results fall under these two subcategories 1) those who admit still having losses, STN, issues and 2) those whos tanks are still too young to really claim that they are successful. What you really want to see are those cases where people added SPS right away and 1 year later they still had good results. Just by reading the different "help my SPS is dying" posts in these forums, I can tell you for a fact that the type of "success stories" that you are looking for is far and few in between. These is why the #1 advice thats been repeated over and over again, and the 1 point in the noobie guide, is "take things slow"
4) if you are looking for a challenge by all means do it. Just be prepared when you run into issues and suffer coral loss. Just based on the help posts in these forums, I would estimate 4 out of 10 who do what you do end up with big issues causing resets, 4 out of 10 will have issues that can be overcome but will have between 30% - 60% SPS frag survival rate. And 2 out of 10 will have q successful run of 75%+ frag survival rate.