I just filled the diesel tanks on my CHB34 in preparation for the imminent bombing of Iran by the Israelis. I always fill until I start to get a burp. From the fill, I keep track of any partial adds and then refill at the end of the season or pending war, then calculate my consumption and rate. Today I happened to stick the tanks and found that the top 5" of each tank is gapped. The filler neck extends 5" down into the tank, precluding it from being fully filled. This causes me to loose a significant range. Is the gap purposeful and if so why? I would assume that a tank vent would allow the gap to fill up, but that does not happen. Also, even if the tanks were full completely, there would be about a 6" neck from deck flange to tank top. All misspelling the fault of my IPad Tom Averill