Sorry it's taken me so long to get back about this. The centres between top struts on a 4th are 86.5cm (so a difference of 4.5cm) And there's easily enough adjustment on the strut brace to suit, as the adjustment is practically on the shortest setting on my 4th. There's 3cm of usable engagable thread on each side.
I other words, I'm pretty damn sure it will fit a 5th gen
@nickb 