A canvas roof membrane(and probably with very light framing like a tent framework) would fit into what ASCE 7-02 refers to as "buildings and other structures, flexible " in Section 6.2; that means the gust factor,Gf, will be different from the normal defaut value of 0.85 given in Section 6.5.8.1.
There is a complicated formula given in Section 6.5.12.2.3 to calcuate Gf. So, first please check your assumption of 1 kN/m2 pressure. Or rather multiple the values you get by using 1 kN/m2 by the true pressure that takes into account a different gust factor.
As for the distribution, what you are describing sounds like a "sail" without further description, as one of the others above stated.
I would tend to treat the frame as a "sign" or "parapet" in order to get the pressures distribution (See Sections 6.5.13 and 6.5.11.5) and Commentary Section C6.5.8 on page 283 and Figure C6-9 on page 305).
The frames will probably take the distribution indicated but it is a complex problem and the structure is probably subject to a unbalanced loading which could shift loads to one side of the frame than the other. So I would apply unbalanced loading on it.