Butt Blocks

I have after much consideration decided to use butt blocks.

My reasoning is that I can do the but blocks in place so 

• I don't have to store the 16 foot scarfed panels
  
• I can manage 8 foot panels all by myself without calling in help.
• From other Builders work, butt blocks are indistinguishable from scarfs in the end product.

However, my smallest screws are 1/2 inch I suspect that they will just project through the two layers of 6mm ply. 

I think that judicious use of a file / dremel may resolve that little detail.