I think it's going to work out fine in the space shown for the motor well in cockpit drawing in the plans. Because of the 25-inch shaft, I can mount it a bit higher, which will help prevent it from drowning out in big waves. It will still be pretty low overall in relation to the top of the aft beam, as you can see here:
The 25-inch shaft will keep the prop deep in the water, with cavitation unlikely. Mounting it forward of the aft beam will also help with this and with proper weight distribution. The board laying across the skids that the hulls are resting on in front of the prop shows that the prop can't hit bottom before the hulls do.
I've also designed and built the aft net beam in the past few days. I scrapped the idea of using the aluminum pole I had for this, as a wood-composite beam will be easier to mount things to and to finish in a way that matches the boat. I used a V-shaped lamination for the bottom, fit into notches cut in the stern post. The other board is the inner top plate, beveled to fit into the V.
Here is the next assembly step, putting the inner top plate in place with epoxy.
This view of the unfinished end shows the final cross-section of the beam. Built of Doug fir, it's plenty strong and stiff while still lightweight because of the hollow area. The piece of wood on the forward edge that stops at the inside of the sternpost is a teak trampoline lashing rail that will be drilled on 3-inch centers for the aft tramp lacing. I'm using teak for all the lashing rails as the holes will be exposed to the weather and most other woods would rot in this use. The sharp edges of the beam corners will get a smooth radius and then the entire beam will be sheathed in fiberglass cloth.
Here's view looking aft to show how the beam fits. The triangular design with the low, flat top will allow plenty of clearance for the tillers. There's a lot of usable space back there between the sterns and the aft beam. I can't imagine not having a net beam to take advantage of it. Mine will have a drop-down ladder in the center with tramps to either side.
Anchor handling and storage is often overlooked in the building phase of these boats, but any cruising boat, no matter how simple, relies on good ground tackle, and that ground tackle must be accessible and easy to handle. To that end, I've built a custom anchor roller for the forward beam that nicely accommodates my 22 lb. Delta plow anchor. Anchors in this configuration are difficult to stow anywhere but on a roller, as they are bulky, awkward and take up too much space inside lockers. The roller housing is assembled here for fit, but will be removed for finishing before it is then filleted and glassed onto the beam.
Here's the anchor, salvaged from my previous boat, a much heavier 26-foot monohull. The Delta should be more than adequate as the main anchor on the Tiki. If I were buying a new one, I would probably go with the highly-regarded Rocna design. As it is, I have this one, as well as a smaller CQR and a large Danforth. All three will be on board with appropriate rodes. At the top of the beam, there will be a teak block to receive the shank and hold it in position, and a cleat to secure it with a short line through the forward eye.
Another big project will be building the slatted deck forward, between the mast beam and the forward beam. I've decided to go this route in lieu of a trampoline, as it is so much better to work on and will last longer. It will also cost about the same or less, as I have ordered locally-grown select-grade southern bald cypress for the material. I considered teak, like David used on his Tiki 30 forward deck, but prices have really gone through the roof, especially for what little teak is available in my area. The cypress will be lighter weight anyway, and should last a long time with care and proper construction. Below, I have mocked up some of the longitudinal stringers out of scrap wood just to get accurate measurements on the amount of material I will need. The longitudinal stringers will hang under the mast and forward beams. Then deck beams across will support the planking, which will put the top of it about even with the built-in ledge on the aft side of the forward beam, making it about 3 inches higher than the adjacent decks on the hulls. The whole assembly will be easily removable as a single unit to aid in disassembly of the boat.
