I decided that it was time to drill the pitot tube mast mounting hardware to the left wing.  I solicited some help from Tami to mount and cleco the lower outboard wing skin back onto the wing.  Once we got the wing skin clecoed, we took the top wing skin off.  This allowed me to cleco the pitot tube mast reinforcement plate to the wing and back drill the reinforcement plate to skin holes.

My last building session, I drilled the four holes to the reinforcement plate that attach it to the wing spar.  I also laid out and drilled 8 holes (4 on each side) the length of the reinforcement plate where it is riveted to the wing skin.  The 4 reinforcement plate to spar holes were used to hold the plate in place to start drilling the reinforcement plate to wing skin holes.

From a head on shot, it looks like the edge of the reinforcement plate runs parallel to the wing rib.  You want this bracket to hold the pitot tube as straight as possible with respect to the air flow over / under the wing.

Just drill and cleco as you go...

Once I got the 8 #40 holes drilled that rivet the reinforcement plate to the wing skin, I drilled the 4 holes that are used to secure the pitot tube mast to the wing with #8 screws.  Those 4 holes are drilled with a #19 drill bit.

Now for the point of no return....  Cutting the hole for the pitot tube mast.  My plan was to shape the hole using a rotary file bit in the die grinder.  To get started here, I drilled a hole in the center of the mast cutout with a unibit (stepped drill bit).  Then I shaped the hole roughly with the rotary file bit in the die grinder.  Those bits are really aggressive and FAST.  So, when I got close to the final shape, I broke out the Dremel Tool with its rotary bit.  The Dremel tool is not nearly as aggressive and gave me more control to make the final shape.  To finish it off, I smoothed out all the edges with 400 grit sandpaper.  Below, you can see my "rough" cutout.

This is with the pitot mast roughly held in place.  There is a slight gap around the mast.  On my mast, there was a slight lip on what is the bottom edge of the mast.  So the cutout shape on the reinforcement plate (and wing skin) had to be slightly re-shaped.  When the mast finally fit through the hole, this is what I have for gap around the pitot mast.

It looks like a big gap in the pictures, but that gap is not really that big.  That said, I am still glad it is on the bottom of the wing.

Yes, in the picture, the pitot mast is still there.  When looking at it straight on, you can see that there is no visible gap.  Not pictured here (see last picture on page), I drilled 3 additional holes on the aft side of the pitot mast reinforcement plate and skin.

Gretz has you fabricate an angle to attach the reinforcement plate to the wing rib.  This angle is not supplied with the kit.  I found some .032" aluminum called out in the instructions from a access cover plate I screwed up earlier.  I have learned to never throw away parts I have screwed up.  You never know when you can scavenge material from them.  Anyway, I took it to work and put it on a brake to bend my 90 degree and used a metal shear to cut it roughly to size.  As it turns out, I trimmed it more when I got it back and dry fit it to the wing.  I ended up trimming material off with the band saw.  A little tweaking here and there and it turned out great.

I just lined up the support angle where I wanted it, clamped into place and drilled them to size #30.  Gretz leaves those hole sizes up to you.  He really doesn't specify.

Okay, all holes drilled and mast hole cut.  After looking at this, I should have really mounted this pitot on the other side of this bay (to the right about a foot).  That is where other builders have put it.  It is still further outboard than what Van's drawings show for their stock pitot tube.  I don't foresee any operational issue here.  It will definitely be outside of the propeller wash.  The only potential issue I see is that it may be harder to plumb tubing since it sits right next to the inboard rib for that bay.