It's down to your personal preference - you want to avoid an additional pin or you want to avoid high volumes? Personally I prefer to make two injections with smaller volumes, but it is my personal preferrence because I don't like to pin to much at a time. As you have seen from previous posts, other people don't have this problem, so they inject all at once. Therefore, there is no problem with mixing these two compounds, and it is just a matter of what fits you best.