Project property changes

Please could someone give me some tips on changing project properties based on this scenario:
Working in 3ds max at 720p and then moving to Hitfilm for post effects. Once approved ( which takes a while and generates plenty of material) I would like to move to 1080p including re-rendering the source source from 3ds Max.
At this point, there are some pretty unique post effects applied to the original 720p material - some of which may obviously have to be reworked. What - if any are the dangers in switching the project properties to 1080p - importing the higher res material and copy / pasting the existing effects and then deleting the 720p source
Also, if I directly replace the 720p material with 1080p versions is there a memory issue or anything?
Thanks for any tips