Day 8 Making the strong back
We decided to make the strongback out of 4x4 treated lumber as it is less expensive than doubled 2x6 and is available. Putting it together was the easy part! Getting it all perfectly level was another story!  
Using a time tested method we obtained reasonable accuracy (we think!) as the 4' level couldn't find an error. Fill a transparent hose with water and decide on a height above the highest point of the frame, then lowering or raising the other end also on a ruler, until the high end was at the decided level. This would then tell us how far the other end point was out. We then raised the beam with metal shims.
( Finally found a use for all that stainless steel flat bar we had laying around that we never used! ) This was done at various points around the frame. The true size of our sailboat to be has become apparent at this point. We could have made the work area a 'bit' larger!

Day 8:
9 hours - Built and levelled strongback