These fifth, sixth and final pair of bolsters were constructed in-house by the Railway Company in 1910 and later dismantled, the frames becoming G.17 and G.18 respectively in 1918.  The rendering below illustrates how the bolsters were operated in pairs to carry longer loads such as telegraph poles, signal posts and timber baulks.  They were short lived and only lasted nine years before being reused, the earlier examples surviving much longer.