Question: Use of results of codegen[optimize]

I have a series of formulae arranged as a vector.  I need to do two things to this vector:

(1) Optimize it using 'tryhard'.  

(2) Use the optimized results to create a new procedure.

I can do either (1) or (2) alone, but when I try to combine them as one command it never works.  A simplified example of what I'm attempting with the resulting error message is below:

with(codegen, optimize, makeproc);
V := Vector(4);
V[1] := x+y;
V[2] := x^2+y^2;
V[3] := x^3+y^3;
V[4] := x^2+y^2+x+y;

T := makeproc([optimize(V, 'tryhard')], [x, y]);

Error, (in codegen/makeproc) Unrecognized input [t78 = x+y, t73 = y^2, t74 = x^2, t77 = t73+t74, t1 = (Vector(4, {(1) = t78, (2) = t77, (3) = t73*y+t74*x, (4) = t77+t78}))]

It seems that makeproc cannot handle a combination of optimized assignments and a vector of formulae.  Is there anyway to fix this?

Thanks