I went with M80's as I was Ok with the length of the tab but had minimal width to work with (8 in wide 10 in long). I placed my tab on the outside of my kicker 3 inches from the outside chine. I would have prefered M120's on my 18.5 DE but it would have touched my kicker. They say the batwing profile of the M series tabs is more efficient as the water will not flow off the side of the tabs, perhaps this is the case. My boat used to fall off plane at 23-24 mph now I can grind through the slop with a slower planing speed of 15-16 mph. This makes a big difference in not having to be on and off the trottle in good size chop and swell.
Similiar to your problem, my buddy went with 9x12 Lenco's on his 18.5 ft Seaswirl as he has the width to work with but not the length - longer tabs touched his swim ladder and kicker (tabs 12 in wide 9 in long). He had to move the Lenco tabs closer in to the center line than what they recommend (e.g. more than the 3-4 inches from the outside chine) but it had no harmful effects, they work well. He ended up installing the port side tab just inside the kicker, about 10 inches from the outside chine, and did the samle on the starboard side.
Not sure of the size of your Malibu. I suggest making a cardboard cut out of Lenco's 9x12 and M120's and seeing where they fit best and how it impacts on your kicker. Take the time to confirm where the actuator will connect to the transom and where the wiring/hydralics will come through the transom on the inside. You may find you may need to move either of the tabs from your current tab location to fit right. If thinking Bennett, look for a space for the hydrallic pump while you are at it. Send me an email if you want some photos of my installation.
