found this video on youtube about putting one together - don't know if it would help.
http://www.youtube.com/watch?v=TNE3As-yctA
As far a the triangle size - an equilateral triangle - where the two short sides are of equal length are subject to a basic math formula - the measurement of one of the short sides multiplied by 1.414 is the length of the long side. Conversely, the long side of an equilateral triangle divided by 1.414 is the length of the short side. If you divide the base of your triangle - 16.5 by 1.414 you get 11.66 inches, which rounds up to 11 and 5/8 in quilters terms ....or the short side of 11.5 multiplied by 1.414 is 16.25 or 16 and 1/4 inches - It sounds like either the designer is pre-trimming your dog ears/rabbit ears for you or the instructions are wrong. working it out on paper should tell you which it is.