Installing 50m2 of reclaimed solid oak flooring - advice required

Hi,

I am looking for some advice on installing the above.

We have bought 60m2 of reclaimed solid oak flooring (incl wasteage) which is in very good condition having only been laid for one year. We have spent some time cleaning and denailing it in preparation for laying. It will be sanded and laquered after laying.

I have just finished building an extension which approximately doubles the downstairs floorspace and our plan is to cover the full floorspace with the oak.

The old part of the house is floorboards which are in good condition and are flat. I have just finished screwing every board at every joist to reinforce and reduce any creaks. The new half of the house is new 18mm t&g chipboard.

I plan to lay the oak diagonally throughout the house (I appreciate the additional work and waste).
I plan to lay a 2mm foam underlay to further reduce any potential creaking.
I plan to secure the full floor with tongue tite screws as this is more convenient for me. I would need to hire a nailer over a few weekends where this way I can spend every evening installing screws which is less noisy and less expensive (I have done the sums). I also believe the screws will be better in the chipboard than portanails.

I guess my question is...
Does this sound a good plan?
Is there anything else I should consider?
Is there any harm in either using underlay or full install of tongue tite screws?

Your advice is most welcome.

Thank you

Mark