My 642 is stern-heavy. It has a 4.3L fuel injected V-6 that makes a reported 220 hp, and I have dual batteries, a 13 gallon water tank, and some additional gear. With two folks onboard the stock boat with no tabs planed just fine - about 5-10 seconds. With four folks and the stock three-blade 19p prop, the boat would take 20 seconds or so to plane. With six folks I'd have to get two persons to move up front into the cuddy, and then it'd take 20-30 seconds or sometimes even longer. I switched to a four-blade 18p prop and that helped a lot, making it possible to plane in about 15 seconds with four folks, but six were still a challenge and we always had to move folks around. The other day, with these 10" tabs and their 90-lb springs, I was able to plane faster with four persons than in the past. I was even able to plane with 7 folks after moving folks around. ALSO -- huge benefit -- I can now actually trim up to 3/4 trim on a plane without porposing. That's something I could not do at all, even with just two on board in the stock configuration. The boat seems to cut through waves better. On my boat, the effects are not as significant as the videos seem to imply. There are several reasons for the 4 stars. One is that I ordered through a third party vendor and not all the parts were present in the box when it arrived. The order arrived about 7 days after it said it would - then I had to call and get the third party vendor to ask Bennett to deliver the parts to me directly, which they did, but it took another week or so. Over three weeks after ordering I finally had trim tabs to install. The service was good - super nice people - but the execution was subpar. Another reason for the four stars -- the tabs helped but didn't cure my issues. I will be placing the tabs on the highest setting before my next outing -- but best I can tell, they helped with slow speed stability, trimming, and planning to some degree. But they also feel like not nearly enough. It's like my boat is too big and the tabs are having subpar effect. I'll try and chime back in after I go to the highest setting. What I may need, at the end of the day, are the hydraulic or electric tabs that are fixed and not sprung. Although some say they can install these tabs in 20 minutes, I personally set aside about four hours to install these. The first hour was just me contemplating the absolute best spots for installation. The second hour was me marking and measuring holes several times to ensure accuracy. I installed the lower hinges for each tab in hour three, using lots of 3M 4200, and that's just half the battle. It's great that folks say this process is quick -- but my advice would be -- TAKE YOUR TIME! Do it right. Use a lot of sealant. Use good sealant. I checked with my dealer about my lifetime hull warranty and if installing the tabs voids that. They said it would not void the warranty unless the source of the breakage was determined to be related to the tabs. In other words -- if you install incorrectly and the interstitial walls of your transom fill with water and rot your wood, etc., don't count on getting that covered under warranty. Also, if your transom is rotting and you happened to install trim tabs correctly, you're probably out of luck there, also. Having said all this -- I still have one more notch and these tabs did help. I consider myself someplace on the spectrum of the natural progression every boater takes as they fine tune their ride to match their lakes, style of boating, passengers, etc. It might be that I need to go with a fixed position tab, but if 90 percent of my woes are resolved through the active tab system, I'm okay with that. I remain hopeful these tabs are the answer. If they're not, they were worth it as part of the progression. Hope this helps!