A way to compensate for a bike that is too long is to go to the drops. I was there a lot before getting a shorter stem. After the effective TT length was adjusted, I had to remind myself to go there. I even flattened out as though I had TT bars. (So the reach was so long, it was as if there were TT bars on the bike). Can't do that now, the reach isn't long enough.
That makes sense. It puts less strain on your upper back and neck than doing weird things to try to hold yourself up. I keep wanting aero bars for the trainer.