Just an update....
I have mounted 24 inch Bennett tabs on my 2320 to replace the 12x12 Lencos. The tabs are mounted with #10 screws while the Lenco hinge had used #14 screws. I therefore patched all the old screw holes with epoxy and then mounted the Bennett tabs by using the Bennett backing plate as a template. I lined up the backing plate with the furthest outboard hole over the furthest outboard epoxy patch. I bedded the backing plate in 4200 before mounting. When the backing plate was mounted all the patches from the Lenco tab hinge were covered by the backing plate.
With 24 inch tabs on a new 2320 the upper end of the actuator lines up with a portion of the transom which is not accessible from the inside. As a result you cannot use the standard Bennett 90 degree elbow fitting to connect the hydraulic tube to the actuator, so you must use the Bennett "short trough-transom fitting" (Part VP1146) which was kindly supplied to me by Tom at Bennett. Fortunately even though you can't get to the inner side of the transom at the point where the hydraulic tubes slide through, it should be an easy matter to fish the hydraulic tubes from the transom out into the battery compartment where the hydraulic pump is set up.
In my case I decided as a temporary maneuver to use my old Lenco actuators and preserve for the time being my existing switches and wiring. (I plan to convert over to the hydraulic system at a more convenient time.) Since I am using Bennet tabs with Lenco actuators I needed to mount the Bennett lower hinge assembly (Bennett Parts A1113 and A1115) on my Lenco actuators. The Bennett and Lenco actuators have the same dimensions and both companies make use of this fact in their instructions for retrofitting from one system to another. There is one dimensional difference between the two brands in that the upper bracket on the Lenco actuator has a different screw hole pattern from the Bennett screw hole pattern. To make the eventual switchover easier, I obtained a Lenco upper actuator bracket (Retrofit bracket part #116) which has a screw hole pattern that matches exactly the Bennett actuator upper mount hole pattern. Thus when it is time to switch to the Bennett actuators, it should be a simple matter of setting up the hydraulics and attaching the Bennett actuators to the tabs and transom. Using my old actuators involved attaching the Bennett lower hinge bracket, attaching the new Bennett compatible upper bracket, splicing some 2 conductor electrical cable to replace the cable damaged when the actuators were removed from the old tab installation, fishing the new cables back to the existing wiring, and making new connections. Next step, say a brief prayer, power up the system, and bottom line, everything worked perfectly, at least on the trailer.
At this point he upper ends of the actuators are mounted to the transom approximately 6" inboard from the original location. Thus the old holes (3 screw holes and a central hole for the electrical wire) from the upper end of the actuators needed to be patched. These 4 patches are the only external evidence of the change over. I still have to gel coat over the epoxy patches, but that will be a separate project when I can batch together all of my gelcoat repairs.
For now I am excited to take the boat out to see whether doubling the trim tab surface area will make a substantial improvement in performance. Stay tuned....