HI Richard, The placement of the dinghy is a personal thing and I agree with everything that Doug said above. However, I would like to add that Mike Pearson lost his dinghy forward because it was not tied down while off shore. I have sailed with a Montgomery and several other types of hard dinghies. I tried the dinghy on top of the cabin and found it was too obstructive of my view and more difficult to deploy and get aboard. If you intend to put the dinghy forward, you should have a dinghy with removable seats so it will set low as possible over the scuttle hatch. This is a problem with the Fatty Knees and the Montgomery, they both have the floatation in the seats. If you intend to use a floatation collar, this will act as your floatation. You could remove the fiberglass seats and leave just a shelf to set removable wood boards for seats. This would only be necessary for the back seat and possibly the middle, depending on the dinghy.
I would like to explain what I use and love. I have my 7’ Cherub set on the foredeck. It sets flat on the deck and is only a few inches taller than the scuttle hatch. On deck on either side of the dinghy, I have flush, through bolted eyes to lash the dinghy down when in open waters. This dinghy WILL NOT COME OFF THE FOREDECK. In order to make the dinghy set flat or as low as possible, I had to cut the end of the bowsprit off flush with the aft end of the bitts. When the weather is really bad and I have to go forward, I find there is plenty of working space on the side of the dinghy. Also the dinghy provides some protection from breaking waves. At anchor, I raise the forward end of the dinghy so I can open my scuttle hatch. The dinghy acts as a windscoop and keeps out all rain except when the wind is strong. To deploy the dinghy, I lift one side so it sets on the other. Then use a two point bridle to lift it off the deck, over the lifelines. As it goes down into the water, I have a line attached to the lower side of the dinghy that is attached to the lifeline. This line becomes taught just before the dinghy hits the water. The dinghy then sets on the water right-side-up. To raise the dinghy I use the opposite procedure. If you want more detail on how this is done, let me know.
I do not have a floatation collar on my Cherub but I do have 5-6 inch fenders lashed to each side to the dinghy. These are lashed together and have a clip on each end of the rope so they can be easily removed. Also, if you would like more information on this let me know.
Regarding the size of the dinghy. You are limited on how high you are willing to have the dinghy set. Let me mention that you can set a slightly longer dinghy on the cabin if you set it at an angle. You can set a longer dinghy on the foredeck if you are willing the have the stem set on top of the bowsprit, aft of the staysail stay.
If yo want me to compare the Montgomery to the Fatty Knees, I will not do it on this forum but if you email me directly, I will explain.
One last comment. If your BCC has the Dorade Boxes with Cowl vents located near the center of the cabin, a dinghy will not set on top of the cabin unless you remove the vents. Most BCC’s that have the dinghy on top of the cabin, the dorade boxes are installed at the forward end of the cabin.
Sorry this is so long, If you have any personal questions regarding my comments, email me at xiphias37@yahoo.com
Roger Olson