Hello, i have a regulator fitted to the bulkhead for my gas bottles,the end of the hose has a screw on fitting to suit 4.5kg bottles but the area to take the bottles is marked 7kg but the only 7kg bottles i can get have a clip on/push on fitting what do i need to do to convert so i can use 7kg bottles as the price of the gas is £13.50 for 4.5 and £15 for 7kg so it makes sense to use 7kg