I did a little research on the bushings. The Powerflex PF99-116 is a universal bushing from their catalog. It is available from Westfield, and Powerflex directly, including PowerflexUSA here in the 'States. At least it is in the US catalog as a "universal" bushing.
The bushing''s measurements are very close to the current metalistic bush, at 24mm diameter and a sleeve length of 39mm is 1mm longer, but the bush is 2mm shorter to accommodate thrust washers. This should not make a difference in the installation.
The steel sleeve and elastic component is a good setup, especially in the rear. This design, along with the thrust washers, should make for a smooth, low friction bushing.
However, the bolt hole is listed at 12mm, where the bolt diameter is only 10.8mm (7/16"). The bushings in this installation would be torqued down tightly, as the sleeve and are separate parts.
If you are interested in trying them out, I would start in the rear, with 4 of the bushings mounted at the forward chassis mount of the rear suspension trailing arms, using the standard bushings (in good or new condition) at the axle. This should offer some additional compliance in roll, and greatly reduce the wear of the rear axle bushings, without compromising (and perhaps enhancing) handling. Set the rear axle bushings up loose, so that they can rotate.
At $45 a pair USD, they are expensive, but should offer substantial service life over the standard metalistic bush. They may also offer a better ride due to the reduced friction. With 17 bushings required in the suspension, the cost for 8 pair (you can probably use the existing metalistic bush for the Panhard rod) is $360 plus state tax if you are here in the US. For $120, I can buy 20 of the metalistics, but then there is the frequent replacement at the rear suspension at least twice a year if I drive the car regularly.
I plan to order 4 and see how they work in the rear suspension.