We don't know. At most we can provide anecdotal reports on what happens to us as individuals if we do this, but that should not be taken as evidence of general safety.What happens if someone decides to take 15mg reta a week? Is that a dangerous dose or due to side effects it was never tested but safe to do so if needed?
If you are hoping to get proper guidance on the safety of anything on this forum, particularly around things still undergoing trials, or in combinations never studied in trials, you're not going to find it, and anyone that claims that they can speak to it is being irresponsible.
If you are not comfortable calculating the risk based off of the information available and understanding that you are taking your health into your own hands when doing this sort of thing, I highly recommend sticking with combinations and doses that have made it through clinical trials and been approved. There's still risk around long term side effects that are unanswered even then. And all of the risks that come along with buying grey market products as well.