In HLSL, is there any way to limit the number of constant registers that the compiler uses?

Specifically, if I have something like:

float4 foobar[300];

In a vs_2_0 vertex shader, the compiler will merrily generate the effect with more than 256 constant registers. But a 2.0 vertex shader is only guaranteed to have access to 256 constant registers, so when I try to use the effect, it fails in an obscure and GPU-dependent way at runtime. I would much rather have it fail at compile time.

This problem is especially annoying as the compiler itself allocates constant registers behind the scenes, on top of the ones I am asking for. I have to check the assembly to see if I'm over the limit.

Ideally I'd like to do this in HLSL (I'm using the XNA content pipeline), but if there's a flag that can be passed to the compiler that would also be interesting.