My observation here is that you should opt for different toys for vaginal and anal play. Metal and silicone toys can be sterilized - but keeping them separate is a safer alternative - although I admit to violating my own rule on occasion!
For my wife - g-spot toys do not work well anally because of the curve. For anal plat something straighter and softer works best for her.
For me - I don't care for curved toys anally either. I prefer to get my p-spot stimulation through a larger diameter. Once warmed up the smaller end of the Eleven (about 1.75" dia) feels fabulous. It has only a slight curve.
But 98% of the time we use silicone dildos for my anal play. After initial loosening with her fingers - my wife uses the tapered Champlette before the main event - which is usually the O2 Revolution.
The Revolutions large soft head feels great against my p-spot and the shaft tapers down a bit taking some stress of my sphincters.