I am not in the same place as my rule book... the dimensions of the base and the vertical as I recall are to be 4 inches each (at least in the case of a "right" triangle)..... I have always made my gussets to those dimensions even if there is no 90 degree angle in it. Also, I have always put the gussets on the side of the tube that was less than 90 degrees ....
Look carefully at the info too.... the guessets are NOT bo be at the center of the tube(s)...... they are to be towards the outer side of the tube(s).... the outer plane of the tube(s) should be the outer surface of the gusset.
and yes, weld with stitches..... on 4" of length, I go 1/3 weld.... 1/3 NO weld... 1/3 weld.... and, igf the gussets are also used for, say affixing a body panel, there is NOTHING in the rules that says they cannot be of a larger size.... some of mine were 5 1/2" (which equaled more than 4" vertical dimension) up the tube and 16" on the horizontal because it helped to make a safety reytention area for my hands....... these two gussets ran forward