Hi @ChrisDLikesROV, welcome to the forum 
That’s not something we’ve tried, but it could potentially be possible by using a 3D-printed mould to ensure a consistent diameter.
Smaller cable sizes have been asked about and discussed previously here, where the suggestion was to use heat-shrink to increase the cable jacket diameter.
It may be worth considering an adhesive-lined heat shrink for waterproofing and avoiding pull-out and push through, but given your non load-bearing use-case and the radial pressure of the WetLink penetrator’s compression seal I don’t expect they would be particularly significant issues.