Compatibility is best checked by a BHPA qualified packer
The most significant risk is that the reserve is the wrong shape or size to easily come out of the harness compartment. There can be other risks associated with the handle attachment point, and the length of the handle or bridle.
For these reasons, we recommend that you seek advice and help from someone who has been trained and qualified through the BHPA programme. There may be someone in your local club who can help, or you can ask a professional packer to check compatibility and install your reserve.