Passing custom distance matrix to T_Coffee
So I didn't find an answer,but I did find a way around if it anyone else has this problem. It does involve modifying the source code, but even if you don't understand c (I barely do) its still easy to do. 

1) Download source code from github 
https://github.com/cbcrg/tcoffee
Source code is here, view the dependency list - you will need all these libraries to compile the code for the change to take effect. 

2) Add your custom matrix to source code.
Search matrices.h. In this version it is t_coffee/lib/matrices.h
You will see how they are defining their default matrices. Just add your matrix with the same format and give it a name. For example:

int customMT[]={
  4,
  0,  5,
 -3, -2, 17,
  0,  5, -3,  9,
  0,  0,  1,  1,  6,
 -2, -3, -3, -5, -4, 10,
  0,  0, -4, -1, -2, -3,  8,
 -2, -2, -5, -2,  0, -3, -3, 14,
  0, -2, -2, -4, -3,  0, -1, -2,  6,
  0,  0, -3,  0,  2, -1, -1, -2, -2,  4,
 -1, -1,  0, -1, -1,  2, -2, -1,  2, -2,  4,
  1, -2, -2, -3, -1, -2, -2,  2,  1,  2,  2,  6,
  0,  4, -1,  1, -1, -1,  0, -1,  0,  0, -2,  0,  8,
 -1, -2, -3, -1,  1, -4, -1,  1, -3,  1, -3, -4, -3, 11,
  1, -1, -2, -1,  2, -3, -2,  0, -2,  0, -2, -1, -1,  0,  8,
 -1, -2, -2, -1, -1, -1, -2, -1, -3,  1, -2,  0, -2, -1,  3,  8,
  1,  0, -2,  0,  0, -1,  0, -1, -1,  0, -2, -2,  0, -1, -1, -1,  4,
  1,  0, -2, -1, -2, -2, -2, -2,  0, -1,  0,  0,  1,  0,  0, -3,  2,  5,
  1, -2, -2, -2, -3,  1, -3, -3,  4, -2,  1,  0, -2, -4, -3, -1, -1,  1,  5,
 -5, -5, -2, -4, -1,  1,  1, -5, -3, -2, -2, -3, -7, -3, -1,  0, -3, -5, -3, 20,
  0, -1, -2, -1, -1, -1, -1, -1,  0,  0,  0,  0,  0, -1,  0, -1,  0,  0,  0, -2, -1,
 -4, -3, -6, -1, -2,  3, -3,  0, -1, -1,  3, -1, -4, -2, -1,  0, -2, -1,  1,  5, -1,  9,
  0,  0,  0,  0,  5, -4, -2,  0, -3,  1, -1, -1, -1,  0,  4,  0, -1, -1, -3, -1,  0, -2,  4};


Then, search for file tcoffee/lib/io_lib/io_func.c Find the function 

int ** read_matrices( char *mat_name_in)


You will see a long list of if else clauses, add the name of your custom matrix using the same pattern as they do. 

/*Read Header Matrices*/
if (strm(mat_name, "pam250mt"))vector=pam250mt;
else if (strm(mat_name, "idmat"))vector=idmat;
else if (strm(mat_name, "dna_idmat"))vector=idmat;

/*add custom matrix here*/
else if (strm(mat_name, "customMT"))vector=customMT;


3) Save the files, move into tcoffee/src/. Rebuild the files using the make file as described on the github installation. It is here you need make, g++, perl, and whatever else on the list as dependencies

make t_coffee


4) Now, align your file! The only thing here is to use the t_coffee of the source code you just edited, and not t_coffee that might already be on your path. So change t_coffee/src/t_coffee to whatever the relative path to this folder is. 

tcoffee/src/t_coffee rhomboids.fasta -matrix customMT


And that's it!