So, in my opinion,
LEFT
your whole left hand is viable #1 - #4/5
Don’t worry about the proximity of your NExT to the APEX flex in position #1, because they will be at right angles to each other when presented to a reader.
I have
xM1 and xEM in #L0 and my Apex Flex in #L1
NExT in #R0 and my FlexM1 in #R1
I have zero issues with targetted reading
Plus on top of those real world experiences / examples, I have done tests in the past with my NExT in #R0 and I was going to put a FlexMT on the back of my #R hand.
I had no issues with that either ( I didn’t put the FlexMT in, because I thought it was too big for my little girly hands, although it was tempting, because the read range was amazing )
If you go for the MEGA, your whole Left hand would be viable ( and the MEGA, is much smaller than the FlexMT I was looking at )
RIGHT
Ignore the xSLX for the same reasons as above, you should have no issues there
I would look at #R1 easily, R2 probably and (maybe R3, but you would really want to test that)
The xG3 is a bit of an obstacle, and if you are not super happy with it there, that would be a good reason / opportunity to relocate it. ( I have personally removed 3 xSeries, all without issue and I relocated 2 of them with no issue)
If you want to leave the xG3 there, and because your xSLX is in a “less than usual” location, you probably only have one viable location for the MEGA on your Right hand
( I am not sure there are any pictures of the MEGA outside of the DT Club, so this representation will have to do )
Wrists are another good location but may be awkward with some readers…