Good point Ak...especially if your rib balsa is very soft and light...which is what we try to do, build light. A solid sheet rib on the center section each side would help to eliminate that.  

Looks like you're in good shape with the current wing.  Just rebuild the center section and take off the upper outer ribs and sand the spars to the needed dihedral. Replace the outer ribs with solid ribs and then glue the outer panels to the solid ribs. Here's a low tech process if you're wondering how to set the angle... take a strip of cardboard etc. the length of the outer panel and pin it to some balsa you can pin to the board.  Raise one end to the desired dihedral and jig it in place so you can take a 90* angle and mark the lower end with a vertical line. Once this has been done you'll have the angle you need to sand the spars to.  Just cut the vertical line (now at the proper angle) chop off the unnecessary length and you have a template you can use by flipping it over and use to measure the line on each spar of the center section on each side.  Hope this makes sense. I'll draw up a quick and dirty illustration in a few minutes and post it with this post.  If you flip the strip of cardboard (etc.) top edge to bottom edge you'll have the angel for the center spars. Mark each side and sand to mark.

Well...Alfakilo's Dime Scale build has inspired me to try a new contra-rotating prop model of the Fisher P-75A the further development of the XP-75 and was produced to a small degree.  The contract was cancelled following WWII.  So here's my version of the Fisher P-75A.
Check out Alfakilo's Dime Scale build here: Click Here
Tom

Congrats on the Marmalade!  Just checking on the prop...figured you had that in hand.

Ian...love your X-1...just not certain about your red prop???  Did you modify it to be a pusher?  The whole ramp device won't work for a pusher on the original prop.  To make it a pusher you'd have to file the ramp off the front and make a flat bearing surface and construct some kind of ramp or free wheeling device for the reverse of the prop...just a thought!

Mike...might I suggest you fill the squares in the cowling and then cut narrow slots just big enough for paper tubes to slide into with a rounded edge in the front of the narrow slots (a round file is very handy for this). I show how to make paper tubes using white glue and bond paper wrapped around a toothpick, dowel or bamboo skewer for size needed. In the Building Tutorials for Beginners and Experienced Modelers: Click Here
Once glued in you can use a razor blade to trim the tubes leaving a nice gun trough.

Thanks all. I really like the effect of coloring the underlying balsa structure with felt pens. It has made a big difference on the last few models I have built, and I highly recommend it as it adds almost no weight at all.
ian

The build came out looking great, color right on and decals worked well too. Very nice.
Mike

Nice!! Your orange turned out really well!!