Maybe that is the key, spend as much time as I can in area at those tougher intervals, problem is today was 10 min over under so 2 minutes at 283 watts then 2 min at 330 repeated for ten minutes. I made it for 3.5 minutes in areo then I had to give up to postion and sat up. And then the other two sets I was hurting bad enough sitting up that are was out of the question.
You should consider the goals of each workout you are doing to decide your priority as it pertains to your position. For example, if you are doing a tempo ride at 80%FTP for 2 hrs, this is a great ride to focus on long duration on riding in your aero position for long durations. This effort is very close to what you will face in a longer race where you will need to remain aero for long periods.
If you are doing a workout with 2-3 min V02 Max intervals, the goal here is to boost aerobic capacity and.or increase top end aerobic power. If you loose 15 watts in your aero position for these intervals, you are loosing some of the benefit of the workout, so it can be best to do these intervals in the position that allows you to hit the prescribed power, and in many cases the highest power possible.
Your over under session described above, that is a tough session. Sessions like that often have me on the brink of my sustainable power and are a good litmus of how well my 20 min power was set. On a session like this, I prioritize hitting my power numbers over staying in the aero position. I go into every interval with an Aero goal. For example, for the first 10 min interval, I may go in with the plan of holding aero for the first 4 min, then doing 2 min upright, then 4 min aero again. For the second interval, I go in with a plan for slightly less aero time. For the third interval, I may do all the recovery valleys upright. The point is, I try to maximize aero time without sacrificing the power goals. One recommendation I have when doing this is ALWAYS do the end of the interval in the aero position. Suffer through, you have a break coming. The end of the interval, and the latter intervals are the most important ones and those are the moments when the most adaption occurs.
Overtime, continue to increase the time spent in the aero position. You are training to bridge the gap between your aero power and upright power and will always be working on that. Keep the goal of the workout in mind. Not all workouts are about improving your aero power... Some are about metabolic efficiency, some are about aerobic capacity, etc. If staying aero causes you miss the main goal of the workout you are not doing yourself justice dropping your power to hold aero. As you get closer to your race, you want to be more specific and will want to be able to hold your race pace power in the aero position and should prioritize that position.