is it possible to get away with leaving only 200mm gap from the gutter
depends on the height above the roof, strength of mounting structure, slope of roof, how windy the location is etc.
essentially it is possible, but you'd generally need to lower the height of the panels above the roof, and increase the number of brackets used on the bottom row, and possibly add an extra rail in to the bottom panels to mitigate the impact of the increased wind loading.
depending on the mounting system used you may also have to be quite careful about the choice of brackets to match with the tiles to get you the 20cm - ie with shuco systems using the bottom antislide clip below the panel there's not really any room to manouver the panel vertically once the rail's in position, so you need to look at where the roof fixing / rail / clip is actually going to locate the panel in relation to the tiles rather than just assuming that you can locate a panel 20cm from the bottom.
