One good idea is to buy shorts from different manufacturers and design as the seams end up in a different places on your bum. The type of insert also makes a difference. Make sure that the shorts are run in over many hundreds of miles and washed properly a number of times before you first use them.
Experiment with different combinations of cream and inserts between now and July.
Having numerous pairs of shorts may be expensive but a worthwhile investment. It is the quality of the
insert and the fit that is important and not necessarily the material or the manufacturer.
Used shorts can be sent home but make sure that they are addressed to the other half.
Washed shorts will dry on the handlebars in next to no time even if the sun is not shining. It is sometimes useful to take a couple of pegs or even just some paper clips as they are lighter. They can be safety pinned to ones back but will not dry as quickly.