Possible to make my own amp integration cable?

Hi all.

New to the forums here! Hopefully, I'm not asking too dumb of a question.

I recently purchased a 2011 Hyundai Sonata Limited (w/ factory amp + sub), and looking to install my Pioneer X920BT while retaining the stock speakers.

In my old car, I installed the AVIC-D3 and hooked it up to the stock system with an amp integration harness. However, with this car, I've only been able to find the amp-bypass harness (Metra 70-7305). The head unit has RCA pre-amp outputs, but there doesn't seem to be a place to plug that into this harness. Not sure if I'm thinking clearly here, but is it possible to modify this harness and splice some RCA females to make it an amp-integration cable?