Hi New to the site looking for a little advice. I’m building a 3.6 x 2.4m decking area for my sister in law. The decking is coming off a caravan but there is about a10-12 inch slope. I was planning on raising the lowest point next to the caravan on 3posts at 0,1.8m and 3.6, then let the natural slope take the high end dig out a little onto boards without fixing. Is this viable. Also the cost is spiralling a little are 100mm fence posts ok with exterior grade decking joists 47mm x 150mm for the sub frame and internal joists at 400mm deck boards are 2.4m x 24mm. Think the spacing is ok on joists, just wondered if I could use smaller not as thick joists for the internal joists. Any help/advice greatly appreciated. Would also put noggins in. Also attaching with Timberdrive 100mm screws. Thanks in advance attached a couple of rough drawings. Area under an awning using for storage and sofa.