A Stratos with a Mercury/torquemaster seam to run a lot different than a Yamaha or Evinrude. I have run a lot of props on my 200XL/250 ProXS combo.....26 & 27 Trophy, 26 &27 Tempest, 26, 27 & 3-28 Hydromotive Quad IV-X OB, 26 & 27 TXP, 26 & 27 TXP OT-4, 26 & 28 Bravo, 28 TRO4, 26 & 27 Fury, 26 Razor3, these are just the ones I can remember.
The 27 Trophy and 27 Fury have been the fastest ones I have run. The 27 Fury is pretty good out of the hole, the 27 Trophy sucked out of the hole. The 28 Hydromotive was just behind the Trophy and Fury in speed (by about 1/2-1mph) but it was the best out of the hole and carried the load best. Out of all the props I have run, I keep going back to the 27 Fury.

Justin, with the load you described and the temps you said, you may be getting about all you are going to get out of it being realistic. You may play with different props and set ups and find 1 mph more but I don't think you will find much more speed until you get some cooler weather. Just my 2 cents.