While surfing the topic, I ran across two interesting sites and a copy of a service manual for the 10.5mm f/2.8 G lens.
The video I found had to do with adding helicoid grease to allow for smoother manual focusing. Based on the feel of the manual focus, this sounded like a nice addition. The video is at
https://www.youtube.com/watch?v=LhCr8vdLzm4 Long story short, the author stripped the lens down further than I want to do to grease the helicoid. Also, from the service manual I found it warns in bright red text:
Caution：
In case the rear lens group is detached, it is necessary to inspect the resolving power after assembly.
Therefore, if such an inspection cannot be made at service agencies, do NOT detach the rear lens group.
He went so far as to remove the rear elements, the aperture blade unit, and more, and split the front element group before removing it. All in all, the video is missing some key steps such as when the hood was removed. Also, probably much more may have been disassembled than needed to access the helicoids but that is not clear.
The second post relevant to trimming the hood is
https://blog.captivephotons.com/cutting-the-nikon-10-5-fisheye/ The interesting point of this post is that the author detaches the screws holding the hood to manage to move the hood somewhat forward to cut the hood with the lens somewhat out of the way. They thought maybe the hood could come off but couldn't see how.
Based on these three sources, it appears that the front element group can probably be unscrewed (assume but not sure) using the outer spanner wrench slots. From the service manual it appears that may allow the hood to be removed by removing the screws as shown in the post sited. What was not stated in the video but I implied from the things that were not shown was that the front lens group was difficult to remove and that may be why the front element was removed to allow some acetone to be used to loosen the assembly and they had to split the front element to access the threads. Warning as was noted in the video acetone will ruin the plastic lens finish.
So two reasonable methods to cut the hood may be to
1) use a can to protect the lens. (Probably still the simplest and safest if done with care.)
2) the front lens assembly can be removed by unscrewing and hood can be removed next by removing three screws hidden under the rubber focus ring to allow the hood to be cut while not on the lens.
Not sure if number 2 is feasible but certainly looks interesting. (One of the comments implies that the front lens assembly is difficult to impossible to remove.)
While applying helicoid grease is tempting, in the spirit of "If it's not broke, don't fix it" the level of disassembly in the video is a step too far for me at this time.
