Many thanks Image -- that's quite a contraption you've constructed there! Having purchased a combined 3/4 & 3/8 set off Amazon, and subsequently purchasing a 1/2 sparkplug socket (not having realized at the time of purchase of the sparkplug socket (i) that there are different sizes of ratchets and (ii) that my Amazon set actually included a sparkplug socket, we live and learn...), I then purchased a 3/4-to-1/2 adaptor to be able to use the 1/2 sparkplug socket. Based on your advice above, I reckon a 3/4-to-3/8 adaptor would be well worth the price of admission!
