How to fill the gap in the floor?

[MuBuPlu]

I've had to replace a few floorboards in my bedroom.

I've replaced them with these Wickes white wood boards.

However, as you can see, the gap that remains is thinner in width than the other six that have been filled.

I have two more floorboards unused. Can I just saw one of them in half length ways to make up the gap? Is there any harm in doing that?

We're going to have underlay and carpet over the top.

Should I think about plywood / hardboard over the floorboards too?

Thanks.

 

[Secret_Sipper]

All the floorboards I've replaced have had to buzz abit off them due to being imperial equivalents. Just screwed them down as normal. You won't have the Tounge or groove on that one but it doesn't matter.
As regards to hardboard/plyboard. All depends. It can cut drafts down and even the flooring out abit but personally unless I'm putting laminate flooring down it's harder to get underneath them if you need too later on!