Replacement siding gives 2 choices for corners:
a. Square 90 Degree Corner
The SQUARE corner is 3" from center curve on both sides. Its designed for hot tubs that are square at the corner. Because you have a generous 3" it will cover cutting mistakes quite well. Also it allows you to tongue and groove the 2 panels to create a faux One Piece side panel. Once the side panels are in place, you can install the corner and cover many screws and cutting issues. When you remove the siding, you simply start with removing both corner pieces and remove one of two of the panels to expose the whole side.
b. Flex 16" Corner
The FLEX corner is a 16" wide corner that will easily bend. Its made for a 12" radius or less. In most applications, this flex piece fully covers the corner curve. You install the screws. Now you can build each side panels as needed. NOTE: Side panels are rigid, flex corner panel is not.
Usually the sequence to install the flex kit is to install first the corner trimming any excess synthetic. Then the rigid panels are installed. You have several options. Most common is the 2 side panels are installed together and about a 1/2" gap between the side panels and flex corner is made. When installed, the kit comes with 8 filler or gap trim. You install them over the panel to corner gap and everything is covered. It allows you to remove the filter/gap trim and then remove the panels as needed. The filter/gap trim pieces are designed to allow ease of installation and access later.