The failure of fillets is the limiting factor in my design.  I'm trying to fillet between two lofted surfaces, and I can only get a .20" fillet when I need at least .80   This happens over and over. How many times have I seen "fillet operation failed, try a face fillet or smaller radius"  I have tried face and variable many times, they fail also.  I ended up rebuilding the model to make the fillets less complex, but the fillets still have limitations.  I have tried creating a section and sweeping it around, that never blends smooth. I am lucky if one of ten fillet attempts work. Quite often I have to give up and rebuild the geometry then try to fillet again. I have spent many more hours fighting with fillets than constructing the geometry. 

UPDATE 10/31  Bike Frame: It is still a battle with fillets. The top picture is the best I have come up with after hours of attempts. The picture with red shows problem areas.  I need a smoother fill/transition from the headstock to the tubes without the recess.  In the V cutout area, the fillets need to blend to the tube.  This is a problem when CNC machining into foam. I am building left and right parts to make a mold. That area is difficult to sand out any lumps since it's right on the parting line.  Below shows the machined foam, the light blue is foam at the machined parting line.   I appreciate any feedback on a better method to do this.  I spend way too many hours fighting the gods of fillet.  Thanks in advance

SW2014 file attached of basic geometry.