Need to fit a quadrant shower enclosure. Main problem is angle in corner of wall is over 100 degrees. This means one side of tray is away from the wall by about 5 cms. what is the solution? If I fill the gap, surely the shower enclosure would not fit on properly as the arc would be too long.Any ideas? How difficult would it be to chase out the wall and put one side of tray in it? Steve-L