First, why do you require that the block sizes add up to the total number of items?

Otherwise what you get is not a partition according to most definitions. You can somewhat get around this by partitioning into groups and letting one group be a "trash" group that is not output. But for that you must have one distinguished group (as in ordered partition) and the rest undifferentiated (as in unordered partition), so it would be trickier.

Now that I'm thinking about it a little more, though, it may be possible to adadpt how it generates RG-sequences internally to support just that by allowing the value "0" to signify "not included in output," where every item (including the first) can take on value 0. I wouldn't be able to code it up for a while, but it seems do-able.