Hi,
we are using SPO as infocube and DSO. A special situation is the remodeling of the SPO. If you extend your model the system changes the partition and the transfer rules in dev system correct. But after the import in the subsequent systems we have big issues with the activation of the internal transformation from the internal infosource to the partions. Right now we have a problem with the activation of data in the DSO after remodeling the SPO. We receive the correct data in new data table of the partition, but after the activation process the new fields are empty. Remodeling - we are not quite sure - needs in every case a deletion of the content of the partitons. But - we are not sure because this makes no sense in case of extension of a partition.
Regarding your questions about the sizing - we are working with a smaller amount of data and therefore I can't help you.
A remark for using SPO as DSO. The DSO as SPO only support full load from the DSO to target infoprovider. Delta is only possible from the partitions.
Hope this helps you. Feel free to contact me in case of further questions.
J.