Fred Scheaffer

Trees are not planes and have much different physical structure requirements You half to under stand the materials you are working with . Just for example take a one square foot of Kevlar 4 oz per foot . Epoxy the peace and see if you can break it. And if it's a composite structure . You can stand your hole dam big ass tree on it and it's not going any where. Just a semantic example .

But i don't want to diminish fuel capacity Thus the quest !

It's good to remain positive . Thing don't become better without trying something new . Or altering something to improve upon it . That's how the Cozy  and Cozy MK 4 came about.

That's the fun part. Just time , materials and money !

Any change to fuselage size would require testing to determine  if the structure is weakened . The structure can be just as strong without adding more weight. You half to be smart on the construction  Materials used ect .

Not really looking for more space . Looking for more weight capacity .

Interesting topic. My observation is that water boils at lower temperatures at higher altitudes. Thus the temp inside the engine is not seeing altitude pressure . The liquid inside the engine sees one atm above sea level pressure because the cap is rated for 14 psi . One atm above see level. The spring in the cap does not care about higher altitudes . It's not going to lift until the internal pressure of the engine reaches above 14 psi. And at higher altitude the outside temperature is colder. If you are running a electric fan on the rad which has a adjustable temp control to keep the engine temp under control . boil over should not be a problem ! And cold should not be a problem either ! Don't know if this was of  any help ? Just thought i would through it out their .

The Cozy MK 4 is 16.9 feet long . The Velocity XL is 20 feet long. With greater useful load . Larger canard and larger main wing . But the Velocity weighs 750 pounds more. The thought occurred to me that if one were to up scale the MK 4 and keep to the  same build layups . One could increase load capacity and keep over all weight down below that of a Velocity . Any thoughts ?