We'll start with WinISD. Open the program and load your file. From the menu at the top scroll down to "Cone excursion (
PR)" under the Passive Radiator heading and click on it. A red line will be seen at "24". This is the maximum excursion of the passive radiator. From the same menu scroll down to "Cone excursion" under the Driver heading and click on it. A red line will be seen at 12.5. This is the maximum excursion of the sub. In the modelling box, click on the "Signal" tab. Enter 100 in the "sytem input power" box. On the graph you'll see a line with a hump in it. The hump is just below the 12.5 mark. This is telling you that with 100 watts of input power you have reached the limits of the sub with the boost that you have. In the EQ/filter tab, deselect the 35hz 6 db boost that you added. Add another filter that is 35hz 3db boost. make sure only that filter is selected. In the Signal tab change the 100 watts to 208 watts. You'll see the excursion of the sub is at 12.5mm. The end result is by changing the boost from 6 to 3db, you increased the input power from 100 to 208 watts, without exceeding the xmax of the sub. Play around with different combinations so you get the feel for it. Remenber the "hump" can't exceed the xmax of the sub.
The PRs weigh 425grms each and you need to add 465grms each (not 456gms) for a total of 890grms each to tune the box to 20hz, according to WinISD. The 790 wieght would change the tuning frequency to 21hz.
Changing the tuning of the box will not alleviate the driver excursion problem. The problem is too much boost. Find out if there is a spec sheet for your amp that has the values needed to change the 2 resistors.
Is it worth it? It would be to me if the values for the resistors could be found. You have everything already. Just swap out the resistors.