Speedfeed IV-s Stock install on a Winchester Defender 1300?

[Person]

I just received my Speedfeed for my Defender 1300. I have a couple of questions about it though:

1. It came with a black plastic spacer that fits between the receiver and the stock. Do I need to put this in or is this if I wanted a little bit of extra length?

2. On the forend there is a little rectangular piece of plastic that is pushed in on top of the forend. Is this needed or is it just for shipping purposes?

Any info is greatly appreciated.

Thanks,

Person