greetings, I had the same issue with making the boat covers look realistic, most I've seen seem look too bulky and draw the eye . I prepared the plastic kit cover and took ages making a template of the shape required, then I tried using various material to give the effect of a canvas tarp. I tried hankerchief material, silk stuff and the synthetic packing that came with some curtain blinds, this was by far the best as it had a fine canvas type weave, but they all looked crap really. ........ then I was having a meal at a pub when someone commented that the paper napkins were really strong when wet... and an idea formed...so I grabbed a load and tried those. Around the edge was a embossed edge which was cut off, the rest had a texture that looked like a fine woven fabric. I rubbed down the plastic cover and gave it a coat of PVA and draped the paper towel over it and wetted it into place with diluted PVA. With a soft brush I could tease wrinkles and rucks into the paper to give the look I was after. I left the PVA to cure and re-coated with a couple more coats, then when dry used a new sharp blade to trim it...primer, top color, job done.No bulk added, conforms to shape perfectly, lovely, easy, cheap. hope that helps. sorry no pics , boat packed away for move to Lancashire.
regards Jenga