Look for a good brand of regulator.
Morningstar & Victron make good affordable ones .
Better to buy a good PWM only one than a cheap MPPT.

https://www.solaronline.com.au/victr...regulator.html

http://www.ebay.com.au/itm/NEW-Morni...8AAOSwKQ9Z60MG

https://www.solaronline.com.au/victr...regulator.html

Bypass/remove the reg supplied on the rear of the panel.
Change the supplied cable for thicker cable. You can determine what thickness (thickness of copper core in mm2) according to length from this table. http://hobohome.com/news/?p=581
Do not scrimp on cable size! It makes a big difference.