What you need to do is retain the allignment of the original sights, while raising the new setup to be exactly parallell with the old one.
Here's what I did with a similar setup. It needs either a micrometer or a good dial caliper. You'll take a few measurements & do a bit of basic math & it'll tell you exactly what height you neeed for the front sight.
Measure the diameter of the barrell right next to the front sight. Write down the measurement & divide by 2.
Measure the total height from the bottom of the barrel to the top of the old front sight.
Subtract the diameter measurement fron the total measurement.
Add the 1/2 barrel diameter to the answer.
This is the front sight height above the center line of the bore.
Now do the same at the old rear sight.
This is the old rear sight height above the center line of the bore.
Repeat a third time with the new rear sight in the middle of it's height adjustment.
This is the new rear sight height above the center line of the bore.
subtract the old rear sight height from the new rear sight height.
Add the answer to that to the old front sight height, this is the same change you made to the rear sight height, but added to the front sight height.
All you need to do now is look up from a catalog & order a front sight blade that is that height & bingo the sights are in the same allignment as they were originally, but raised equally front & rear.