I would think a careful splicing of smaller sheets would not be of a great detriment, just a bit more work. Carefully sand the edges for perfect fit, using glue sparingly would not add a lot of weight. The resulting glue joints might actually add some stiffness and rigidity to the fuselage. Think about it. You can lay out and glue the sheets together, trace you fuse outlin onto the resulting larger sheet, sand smooth, then cut out and glue to your fuse crutch. Here's a chance to clear out your scrap box and odd bal sheet selection! Just make the joints as perfect as you can.
Type at you later,
Dan McEntee