How to make 'Frenulum Groove' with VLC Tugger?

[Vociferous-2ND]

Hey guys,

Just received [words=http://TLCTugger.com/MOS]VLC[/words] today.
But Frenulum hurts, apparently it requires a groove on the inner cone.

I have emailed the inventor.
But is anyone on here DIY/engineer minded?

Perhaps fine sanding a groove into the rubber of inner cone?
Melting a groove?

Thanks V.