The biggest trouble with the Monogram B-29 is that the entire kit is a pile of shoddy workmanship, but that is not really relevant to this thread, so I'll just point as quick as I can out the worst problem all kits from this moulding have (since you show an interest in getting some kind of accuracy out of it):
What happened here to the B-29 right fuselage also happened to a lesser extent on the Monogram B-24D's right fuselage (but, interestingly enough, not to the B-24J mouldings): A flaw or manufacturing error was made on the right fuselage half, marring the finish inside the mould.
Rather than starting over, as would have been done for any other kit, here Monogram chose instead the subterfuge of "grounding out" the mould flaw, resulting in the entire right fuselage half being "ballooned out", as the whole area of the right fuselage mould was bored out out to erase the flaw.
Here you can see the "ballooning" due to grounding out on the right rear fuselage (left on image):
For some reason the tail is off center as well: This has nothing to do with mould exit cool-down warping: ALL the kits are the same, and this is certainly from the very first 1977 issue as far as I know (please don't mention warping or individual de-moulding issues: This is not what is at issue here):
You can see below here how the right fuselage is ballooned out to the right, making the nose curves seem off-centered, seemingly pushing the nose to the left:
This is why the canopy fits so poorly: A Squadron canopy is an immense improvement in accuracy, but unfortunately makes things worse by conforming easier to the kit's crookedness... Heavy-duty pliers are the order of the day here to try to restore the nose's symmetry... As is shaving down the entire right fuselage surface (to half or even 1/4 thickness in some places) to help at least having a hope of an "impression" of symmetry...
Again, here you can see the much more massive right "cheek" on the left side of this join-centered shot:
The fin is tilted and its root is slightly off-center as well, but this seems to have been done to minimize the appearance of the other various tail problems...
Finally: Both the main wingroot stubs are the exact same depth from the fuselage join on both sides of the kit, so you can see by their different prominence how the ballooning right side fuselage has diminished the prominence of the right side wingroot (here on the left), revealing the true nature of Monogram's fraudulent "fix"...:
As for the Cutting Edge cowlings, they do have their face tilted "forward", and a slight excess of "rounding off" on the front cowling edges, but that can be mostly ground down from the front, and is nothing compared to the utter fiction of the horrible Monogram cowls (or the kit total of 8 identical exhausts instead of the actual 16 different ones while we are at it, Peccadillos at this point you know)...
The Cutting Edge cowls are a little under 4 inch too shallow for the kit nacelles, which forces modifying the kit nacelles shallower: That looks quite accurate, as the kit nacelles are obviously too deep...
Those resin cowls are a pain to fix, but still worth every penny if you want to hold on to any faint glimmer of hope of an accurate appearance...
The very slightly unevenly spaced intake grilles, way deep inside the intake mouth of the resin cowls, are indeed there, but about as significant as a snowflake in an avalanche...
I'll underline that although I have managed to fix somewhat the above symmetry issues (over 6 years of toiling at this), I have never seen such garbage workmanship compromise on any other mainstream high production volume injection moulded kit ever (Monogram's own B-24D excepted), including all other kits from the 60s or 70s that I know of...
This is just to point out if you expect a similar soundness of alignment out of the Monogram B-29 (that you have every right to expect from all the other kits, and for all of them you do get at least symmetrically grounded fuselage radiuses), just be aware that this particular Monogram kit plays by its own rules and is a whole other ballgame...
Gaston
P.S. Oh, and the tailgunner's doghouse is 2 mm too long while the whole kit is one scale foot short (98 ft. vs 99), meaning you have to add 8 mm in the tapering area of the fuselage... Fun useage of a second kit! :)
G.