Hi Longon1980… welcome aboard!
We do see many guys upsize over time on subsequent orders. This can be attributed to gains made wearing the Stealth. For quicker more substantial gains inclusion of some regular PE exercises such as jelqs is recommended.
We will be having a range of more serious PE devices in the near future. These will be top quality at affordable prices and fun to use.
As you are borderline between the D and E series for length you could size up and see what you prefer. I also am between sizes and wear one or the other depending on how I am feeling and what sort of engagements I have lined up for the day.