RE: cardboard airplane plans!
To borrow a phrase from our own Dick Hansen "if it's light enough it'll fly well". This definetly applies to anything model sized with a delta wing. Paul, I suspect the MF's were that way because of the weight added by the extra structure that served no purpose other than window dressing. Granted such a design won't be superb as an aerobatic model but if it's light enough and has some significant degree of power it should do well.