On a related subject that I do have first hand knowledge of is the engine mount "isolators". First I want to say all engines will sag after a short period of operation. However I feel the best you can get is Lord Corp.. The proper part number for the Dynafocal is: J-9613-40 x (4). They are about twice cost of the ones Van sells but think they are worth it. I can't say they will sag less but think you will have less vibration and start/stop movement, which is a cause of a lot of wear on engine parts. If you ever take a Lord vibration isolator in hand and side by side compare, they are a world apart.
I love Van's, but... he does tend to pinch pennies. I am down with that usually where it makes sense. The ones he sells are fine ($55 each), but..... yes they are cheaper. They are made by Vibration Isolation Products. The other brand is Berry Controls, which is middle of the road and cost about $75.00 retail (van use to sell these). The Lord Corp. isolator are about $90 apiece (you need a total of 4 to mount engine), and I think they are worth every penny. They helped my vibration issues on my old RV-4.
If you use the plan bushing for the conical mount, do yourself a favor and get the Lord isolator for conical mounts. Now that is a MUST! They are way better than plan bushings. They do cost more than bushings. Part number J-1552. They cost about $35 each, but in this case you need 2 per corner or a total of 8. I believe that is what Van sells for the conical (in pairs) for $75.
Here's info one engine mount condition and sag.
http://www.lord.com/Default.aspx?tabid=1535
Cheers George