Saving Old Seagulls

I do hope there is a major flaw in this diagram. I made an executive decision to amend the placing of one item ( which takes a lot more assembling than a 102, esp. with ancillaries like wot I've got)

Gave the sage of Maidenhead a tentative ring for enquiry but found I was, as usual, 151st in his phone queue.

Probably being dumb but I can't see the flaw, give us a clue? Having partially dismantled one of these it looks OK ...... ( Except the piston goes in the barrell )

Waggles the question was which way around does the head go?

The motor I had was out of the tray already with the carb off and unfortunately the main parts are now in the caribbean. ( Not actually in the sea tho I hope )

I think the pic is OK tho, the carbie heat shield will show which way up is correct due to the hole for the spark plug? Don't think it would make much difference to be honest, as I recall although the spark plug is angled it hits the combustion chamber fairly central and the head chamber profile seemed pretty uniform if I remember correctly?

After reassembling, river testing and looking at it again,the plugole should definitely face to the left looking at the head (the plug lead comes from that side)
I agree the electrode position is not important, but it is difficult to remove the plug shroud upwards, and crap would lodge in the horizontal fins.
Beside, to the left is where is was originally, and pictures of 170's on Seagullparts are also. I just had a fit of insecurity at the bench . . .