The elevation axis is the axial centre line through big horizontal bearing bolt which holds the dish backing structure to the bracket on top of the pole. Just measure from there down to the lower edge of the dish.

Multiply the distance by 0.088 (which is tan 5 deg)

Starting with the dish front face vertical, that gives the approximate movement backwards of the bottom rear edge of the dish towards the pole. Is there enough space ?

If you know exactly what model is the antenna you can look at the data sheet here

antenna data sheetsDown to 5 deg is likely to be possible.

Best regards, Eric.