Glenn, Ilford is offering only sizes to which they have assigned a specific catalog number in advance, and then only by prepaid order during periodic special order periods to be announced in advance, and only if they receive sufficient orders in a given size to cover the cost of re-setting the cutting machinery for that size.

10x20 is not currently one of the sizes they are offering. Hugo could ask for a catalog number to be assigned for next time, but he would have to wait many months for the next ordering opportunity and then after that for production and delivery. Also, I don't know of any other users of that size, so unless Hugo is willing to place a substantial order by himself - probably well over $1000, if the feedback from this round of ordering is any indication - they won't be able to cut it even if the catalog number is assigned.