Merbeu decking - now close to sides to secure?

[Williamstown]

How close to the sides of my 90mm merbeu decking do I put my screws/nails?

From various posts it seems sensible to use 2 screws/nails on every joist; however not sure how far to put them in from the sides, is 20mm too close given if they are both near the middle there may as well be a single screw?

[Bloss]

I do about 10-15mm in from each edge and at a gentle opposing slant towards the centre of the board (ie: the head leaning slightly out towards the edge as you nail in. The slight angling just gives a little more resistance to uplift from any cupping or twisting of the boards.

Then again I use straight-sided galvanised nails, pre-drill all and hand punch down as I have found that gives me the best result. Others are happy with nail guns and dome headed nails and use the twisted or annular nails for better grip.

In some decks, such as in high salt areas near the coast or around a pool I have used screws - again pre-drilling. I have done a couple of decks using screws for the appearance and ease of access to the under deck area. This also allows easy re-tightening if there is any shrinkage or movement.

[Blu_Rock]

I used S/S screws and put them in 15mm from the edges. See my post here. Where the decking butt joined, I had them 15mm from the edges and 12mm in from the ends.

[Williamstown]

Thanks. I've decided to screw it down and will go 15mm from the edges.Plan on making up a little jig to allow me to get all the pilots in the right/same position.
I had a difficult time sourcing the screws spent 3/4 lunchtimes travelling around the city to different places (including a few fastner shops). The problem was they all had too large of a head and the ones that didn't weren't in stainless. In the end I ended up getting some from bunnings which are only 7g x 50 rather then 9g which I was looking for. They seem to be doing the job nicely and have a very small head - not too much bigger then the nails plus they are marine grade. They were also a lot cheaper (@$45 for 350, rather then $200 to $260 per 1000 which I was quoted elsewhere).

[Williamstown]

Blu_rock
What is that red/purple colour paint looking substance you have painted on the top of your joists?

[Blu_Rock]

The red/purple stuff is a couple of coats of Solarguard, Manor Red colour, that I have applied to all the treated pine timber. In real life, it's more of a reddy/brown colour.