OK so I wrote, very quickly to test monogame and mono for android, a hex (isometric) engine. In XNA worked perfectly in half an hour and I followed the video on utube to convert tomonogame and that worked ALMOST perfectly too.
 
The one issue I had was that my XNA graphics ( a line of 64 x 64 hex tiles ) were no longer being drawn properly. (in XNA PC build they worked perfectly) with the following variable settings ( I assume you understand basic hex maps)

    static public Texture2D TileSetTexture;
    static public int TileWidth = 64;
    static public int TileHeight = 64;
    static public int TileStepX = 63;
    static public int TileStepY = 48;
    static public int OddRowXOffset = 32;

 
I noticed that what the simulator was displaying ( horendously, flashing like a mind control system in a 70s TV series, and causing me head aches and making me want to buy the full version of mono for android so I can get rid of the effect buydeveloping on my Android device ) was something I had witnessed before ( in the distant past, the first time I tried to write a hex map )
 
the offsets of the tiles were wrong. I fiddled, randomly, for a time and got to a set of numbers that worked and allowed the emulator to display what I wanted it to display (plus mind hurting flashing). the following are the settings:

    static public Texture2D TileSetTexture;
    static public int TileWidth = 102;
    static public int TileHeight = 100;
    static public int TileStepX = 102;
    static public int TileStepY = 50;
    static public int OddRowXOffset = 51;

 
as you can see they don't make a great deal of sence, what has happened to my graphics files?
 
unless there is a setting or procedure that everyone in the world knows except me, I thought that this would be a bug I would find mention of in the forums, but I didn't, so clearly I am doing something wrong...
 
let me in on the secret!
 
thank you