i have 7 :1 40mm harkens on my A class, running 6 mm sheet and im pulling over a 9.6m surperwing, they are fine, work great, i have 6:1 55mm on top of a 75mm ratchet on the stingray (basically an F18) and thats more than enough. i would say that 40mm for the mosquito is just fine. the only issue with the 40mm gear is that autoratchet is only available in 55mm which adds about $100 to the price. i bought my 40mm stuff from catsailor.net, arrived in 4 days, $15 postage.