Musicbox3 is about the same size as the Bolger Micro and is clearly derived from it. I've sailed on a couple of Micros. Amazing boat in a lot of ways, especially in the amount of room inside a 15' boat. The volume is the result of a 6' wide beam and flat bottom.
I thought that in most ways Micro's strength and weakness was in its keel - about 450 pounds of lead casting permanently fixed for a draft of about 18". The strength is that Micro is very stable and self-righteous. The weakness is in the difficulties in launching and using a boat with that much draft, and in making the casting. For all the griping about making the casting, I never heard of anyone trying one with internal ballast, or using a leeboard on Micro, both mods would be quite possible. So I tried both on Musicbox3. The ballast shown on the plans is in the form of a water box which holds about 500 pounds of water. That could be replaced with lead or steel bolted to the bottom of the bulkheads if you didn't mind trailering the ballast - it would give more room inside, too. So Musicbox3 should float off the trailer in just 5" of water, and float in 7.5" with the ballast tank flooded, and about 9" with two full sized adults with their junk.
The pivoting leeboard and rudder allow the boat to be driven full tilt over shallows or onto a beach, something you would never do with Micro. But keep in mind that the ballasted Musicbox3 weighs about 1300 pounds and you will have to lift and push that back into the water. I suppose in a tough situation you could pump out the ballast water to float her, as they used to throw cannons overboard in Columbus's day to refloat a grounded boat.
I used a gaff rig on a tabernacle on Musicbox3 to improve on Micro's set up time, and I think Musicbox3 would be far and away the better of the two if you had but an afternoon for sailing. I didn't show a gallows but you could add one such that you can fold the sail rig with the yard, boom, sail, and mast all in a neat package, with all the rigging ropes left installed. Micro's yawl rig is superior for cruising, especially for anchoring in open water. I think Musicbox3 could be tinkered with to add the mizzen mast. To me the best cruising rig might be this gaff with a shortened boom, a small mizzen sail, and a very good outboard motor. Musicbox3 has a small well in the stern for the motor, and a small well in the bow for anchors.
The capacity of these boats comes at the expense of weight and materials - after all, they are 20' boats compressed to 15'. Musicbox3 requires 5 sheets of 1/4" plywood, eleven sheets of 3/8" plywood, and one sheet of 1/2" plywood. She is more robustly built than Bolger's drawings show Micro, but I suspect most Micros are built heavier than the drawings show.