I was going to weld the inner flitch panel in today but while I was drilling for the spot welds and positioning I noticed that the top of the old inner flitch, which is in good condition is loose. I have marked out a section which I was going to cut out and join to the top of the repair flitch panel.

As you can see there is a gap on the LHS and if I push here...

this section moves. Should it be joined under the scuttle area somewhere or is it firmed up when joined to the flitch panel I am going to weld in ??
Also is the bit I have cross hatched where the scuttle closing panel goes against??
Thanks,
Graham