SIG's Bob Nelson is the tech for the Senior & 4Star - perhaps others. I want a cowl on my Hog Bipe so I tossed him a request for info. He did the research and confirmed that the Smith Mini firewall and the Hog Bipe's firewall are the same and that the Smith Mini cowl would fill the bill. Ya gotta love the openness.

I have covered 2 1/2 planes in Ultracote. The 2 are my 4*60 and a Sky Raider Mk II. I balanced both fully assembled but without covering of any kind. After covering the Mk II and WITHOUT moving the battery or servo tray from their pre-covering assembly I would have had to add 4 oz of dead weight to the firewall to achieve the same balance. I was very surprised at the amount of weight shift of the covering. I guess that the surface area of the tail feathers places a bit of weight at the extreme end. My LHS owner (one hell of a builder that use Ultracote exclusively) has used Ultracote Lite on his gliders for weight savings - but he cautions that covering skills need to be pretty good because the Lite stuff is not as forgiving as the standard stuff.

When I built my 4*60 I balanced the balsa stock used constructing the wing pieces so that they balanced a tad bit heavy on the starboard side to offset the muffler of the upright mounted Saito 91. I'm guessing that you could easily see a 1/2 lb. overall weight difference solely based on wood selection - using the lightest balsa available rather than the balsa supplied in the kit. I don't really care about this level of detail simply because I'm a rookie flier that needs reinforced structure (survival) more than I need bragging rights to the lightest plane at the field.