P5 flooring max expansion gap?

[Digmixfill]

I'm measuring up to fit the first of my P5 flooring. The room length is 4250mm, so 50mm larger than 7 boards. 25mm gap at either end and no slicing boards in half.

 

What is the maximum expansion gap you would accept before you decide to start slicing boards?

 

[Oz07]

25 be ok but might have acoustic implications. Probably find it's a bit less than 25 with the tolerance on boards and joints not being 100% tight