I have one 1911, a Les Baer, with the GI rod ...and I haven't replaced it ...but I think without the full length guide rod - there is a chance the spring might kink...
Can't do it.
Marketing 101: Convince the customer that he needs it...and then sell it to him.
With the slide in battery, there are only 5 or 6 coils between the end of the guide rod and the end of the spring plug that are unsupported. As the spring compresses, its OD becomes captive by the plug, and its ID by the rod. By about 1/2 inch of slide travel rearward, the spring is captive. At full slide travel, it's completely encapsulated by the plug and supported in both directions.
Here, the end of the plug and guide rod can be seen, along with the unsupported spring coils. There just ain't a lotta room for the spring to bend.