John/Spiros, thanks for your comments... ;-).
Some additional photos now - the first one shows the engine with its horizontal mount in place. That engine mount should slide through the sides of the vertical frame next to it and the small support goes under the engine mount at the front. However, I mentioned in my first post above that the vertical support was misaligned and while trying to sort that, I broke it in two! This goes to illustrate that these pieces can be easily damaged when working with them, and indeed, when trying to remove them from their 3D-printed support structures so whichever way you choose to separate them from their supports, or when working with them thereafter, please take care. Not being technically minded, I wonder if perhaps these items could be spaced a bit further apart on their supports? That would be very helpful, but perhaps bigger support stands come with their own issues.
Anyway, onwards... I got round the problem by leaving the broken support out of the build, and therefore the very small front support as well; the engine mount has a notch either side which aligns with the ribs inside the fuselage and with care, the engine mount can be brought into position successfully - without any adhesive, thus allowing a little wriggle-room to achieve the correct sit of the engine - when closing up the fuselage. I should add that I shaved off a small amount of the engine mount piece at the rear to ensure it had slightly more space around it, thus allowing for it to be correctly placed.
All corners and edges of the cockpit frame were carefully rounded and adjusted so as to get the best fit between the tabs holding it in place; the two ultra-thin spars at the bottom of the ammo box did not survive my efforts to get it into position, so I lined it up with its position in the opening on the right side of the forward fuselage, then applied adhesive from the inside to secure it against the cockpit frame. Seatbelts were painted and attached - two over the back of the pilot's seat, and the two side belts anchored at the rear frames the seat sits on. These pieces are provided in the kit. The control column, fuel pump and a small part with levers as well as the pedals, were all attached at this time. I glued the instrument panel on the opposite side of the fuselage so as to leave a little space for my hands and fingers to negotiate the rather restricted cockpit area as I went along.
Some of the detail is really good on these internal pieces, although sadly not much of it will always be visible on completion; I especially liked the 'bullet' detail in the ammo box under the feed arm, the handle on the control column, the cockpit frame's various attachment bolts which look good when highlighted with a little metalic paint and some blackwash, and the double covers on each of two of the three pairs of engine cylinders. The discarded engine support is not any obstacle to the detail of the interior because, from looking through the cockpit, the instrument panel and ammo box obscure the location where that part should have been, and similarly, the engine itself blocks any view of the piece's intended location when viewed from the engine chamber. The lost cylindrical part from the bottom of the carburettor also goes unnoticed when the engine is enclosed in the forward fuselage. So, all in all, nothing that has gone slightly awry so far has had any tangible effect on the process which will end with the closure of the fuselage halves.
So now, I'm off now to do just that, starting with the front area of the fuselage and once that is secure, I will draw the rear section together. The fit of the fuselage underside join leaves a bit to be desired, but careful sanding will achieve a better opportunity of good alignment; I suspect some plastic card and filler may come in handy in completing this area successfully. I will be sure to wear a mask for that work, as I'll be using my handdrill with a sanding disk attached and nobody wants to be filling their lungs with gunk as a result of that work.
I hope you like these photos and more to follow in due course... ;-).
4 attached images. Click to enlarge.