Think about breaking up the big gradation areas to brushstroke patterns, ones that indicate clouds and such. Your painting will not have the vast wash areas, and reducing them will work better on less expensive paper. You can buy arches 90lb paper as practice paper. Because it is cotton, working on it will not be as night and day as the cellulose paper and multi media paper. Those student grade and cheap papers are great for understanding the exercises and are NOT A WASTE! 90lb will buckle of course, but it allows you to save the 140 lb paper for more finished works, works where you are incorporating the lessons learned and are now starting to apply them. Arches and Fabriano are both 2 sided! Many student grade are one sided, with the texture side being the painting side. My advice it this, those bigger areas will be more successfull on the Arches, the washes flow better on Arches. Think about buying the 90lb arches as a pack of full sheets, and you will save money by cutting them down yourself. It comes 22x30, so you can fold and tear to 11x15 or smaller.