Thanks for your comments.
Yes, you can use the components in different combinations to suit your purpose. Ideally you would not experience any slippage with just the Innerwear, a single spandex sleeve and retainer band. You can work with what you have and then make your next size selection based on what you think will improve your experience over what you have now. These decisions are based on personal observation so pay close attention while evaluating the performance day to day.
Yes, I understand how irritating the sensation of retraction can be. You should be including some manual jelqs and stretching as well to counter this tendency. The Corkscrew will also be useful to actively stretch the penis for more active extension training. Of course, the new Vac-Hanger will be of great benefit for the most intensive hanging sessions and longer duration low intensity training as well.
The penis will be trained over time to hang longer but for the best results you should be including the above mentioned exercises for a more complete and holistic approach to your PE regime.
All the best.