I'm going to be contrary.

Range check the radio on the ground with the engine running and stopped. If it range checks fine, it's fine. Unless you are in the habit of flying nearly OOS, it won't matter.

Antenna's aren't that finely tuned on any RXs these days. In theory you want a fraction of the wave length. But if you notice, the same RX and antenna is sold for channel 12 and for channel 60. In theory, the antenna should be differnt, but it isn't. So 2-3 inches won't matter 99% of the time.

Some RX's can have up to HALF of the antenna removed with no problems. See:

https://www.fmadirect.com/site/fma.htm?body=FAQs

and click on Receivers.

I don't know about your JR RX for sure, as I don't know how sensitive JR RX's are to the antenna. I know I've not paid that much attention to the antenna length of position on my JR's and I've never had a problem.