Octy II Rear PDC problems

Just had me new Octy II elegance estate fitted with a Witter towbar , and have now found that it has upset the rear parking sensors. :thumbdwn:

Have established however that If I cover the two sensors towards the centre of the bumper up with my hands that it stops the eratic bleeps. :confused:

Could it be the shadow of the Towball causing them to go mad?

Therefore does anybody know if it is possible to disable the two (inner) of the four sensors thus allowing the two outer sensors to still work?

cheers

Jonny Baby

PS had a removable bumper protector plate fitted and this works a treat, very neat