I sent an enquiry to Dow Corning, this was their response:
Dear Mr. Wyatt,
Thank you for contacting Dow Corning.
The only silicone adhesive that could develop adhesion to silicone rubber is our DOW CORNING® 732 MULTI-PURPOSE SEALANT. More information ontis product in the data sheets (below and attached):
**LINK**
You can contacrt our channel partner for further support:
Univar Specialty Consumables (UK)
Tame Park, Vanguard
Wilnecote, Tamworth
Staffs. B77 5DY
Curiously enough, I used to live very close to there!