Here is another YFG model that I have never seen before, and isn't mentioned in my '95 German edition of Kuebler - the YFG-30XL:
Unlike the regular YFG-30, which was made in Japan, the XL model was evidently manufactured by the Yamaha plant in Singapore. Its beam is the same width as that of the regular model, but the external groove is much shallower, and the racquet is somewhat lighter overall. The frame itself is essentially the same length as the standard model and is dark brown, not black. As far as I can tell, the only meaningful difference between these two sibling models is the grip length. Consequently, I think the "XL" refers strictly to the "extra-long" grip and nothing else. This would then beg the question - Were there other XL models in this product line that came with the longer grip, or were the two-handed backhanders back then given only this one single special treat by Yamaha?