I would imagine that the wall thickness would be the most important thing
You'll almost certainly be able to make allowances for the extra 3mm OD when you fabricate the jig
Just measured a piece of standard UK spec 5" pipe
The wall thickness is 4.9 mm & the oD is 127.5 .... As steel sizes are nominal, I would not be surprised to find a piece of 5" pipe with an OD of 130mm nor as little as 125mm
If the wall thickness is there, I would say, go for it.