Most likely you will need to adjust VTA on your RB303. I use Acoustic Signature Rega Spacers with great results:
Adjusting the height of your Rega tonearm is easy with Acoustic Signature's Spacer Set made from Stainless Steel.
It allows you to adjust the height from 0.5mm to 3.5mm in precise steps of 0.5mm - without removing the tone arm.
Loosen the screws, insert the spacer(s), lock the screws back down, and your tonearm is ready to play.
The set goes for $95.00
Happy listening!