I have found the use of one to be well worth the trouble and expense. I bought the new Z18 with 150 four stroke and it performed perfectly- but fully loaded with fuel, livewells full and two big guys and the gear you can tell that hole shots were a little slow and very much fuel consuming. Since I had run the SE300 hydrofoil on a 20' glass boat with the 200 Yamaha I quickly put one on the new engine- absolutely a good move for me. On plane easily every time with 3000 rpm or less throttle. That, in itself, is worth the investment. The SE300 comes with a very well thought out template to do the install directly to the cavitation plate. don't even consider the clamp on system- they don't last and are expensive. There really is no issue with drilling the 4, 1/4" holes in the cavitation plate. I've used the model I've mentioned for 6 years now without issue. You will see mixed reviews on the use of one but I'm not going run without one. No matter what else you do with your prop configuration- you will see great improvement in the boats ability to get up out of the water and go- especially with heavy load situations. You will also be able to hold plane at lower RPMs. Ive never experienced any kind of speed increase with the use of it- Z18 set up properly, tops out at about 60 depending on conditions- that didn't change but I knew that it wouldn't. Since I fish a lot of shallow water here in Louisiana I am also using the Atlas Hydraulic Jack Plate on the Z18.
Keep in mind that you shouldn't use one combined with any kind of hull attached planer boards or stabilizers since they can counter act each other making for some strange handling characteristics. Ok, that's my 2 cents worth....
