[elmokki]

Also the modding document is very clear on how to combine slots (see 7.11.2). If you understand binary, it's also pretty easy to see that 2 hands is sum of 1 hands and an unlisted value (4) for extra hand. 3 hands is sum of two hands and yet another unlisted value (8) and it goes on for 4 hands (16). These are binary numbers in decimal which are summed up for things like terrain types or random pick path masks too. Why? Because you can always break sums of binary numbers expressed as decimal numbers to the individual binary numbers so the one number tells the game all the terrain types or all the magic paths in the sum.

Basically you could list it as:
First hand - 2
Second hand - 4
Third hand - 8
Fourth hand - 16
Sum up for combination.

Due to how this is done, you can only choose one line per slot type from the list. So you are limited to 0-4 hands, 0-2 heads, 0-1 body, 0-1 feet and 0-4 miscs. If you really want to experiment, you can try adding 65536 to the #itemslots because that is the first binary number expressed as decimal number that is not used judging by the item slot list, but I doubt it'll do anything.

Theoretically you could also try summing up things in the style of fourth hand + first hand from my list above for 18, but what's the point when that's two hands just like the 6 that is guaranteed to work.

Someone may wonder why it's not worth it to try combining something like 2 + 3 hands for example for 5 hands. The sum of those values is 6 + 14 = 20. The reason to this being obviously infeasible is pretty simple. 20 is the expression of binary numbers expressed as decimals 16 and 4 summed up, resulting (see my list above) in adding second hand and fourth hand and probably resulting in either two hands, crash or no hands at all.

One binary number can appear only once in the mask which is the reason to above. Summing up 6 and 14 is stupid because it basically means first hand + second hand + first hand + second hand + third hand. Similarly you can never get two bodies because 1024 + 1024 = 2048 which is the number for one pair of feet.

Of course if someone has patience, go ahead and do experiment, but the table of item slots is certainly not encouraging for experiments.