I've not done this in probably 25 years, so memory is a bit foggy, but don't recall the trick being effective only to go down in frequency, but rather also up. And what I do remember clearly is that it is very important that first of all you need to enter ALL frequency (7) digits (even if they are trailing zeros), and secondly it is also vital to remember to momentarily let go of the shift button when entering the period (.) into the frequency, otherwise in either case the RSS will reject the entry and revert to displaying the previous frequency.
Also probably worth mentioning is that since the VCO voltage also controls the adjustment/tracking of the RX stages, its important for that to work right, as depending on the target frequency you may still have a decent VCO lock but the receiver sensitivity might not be very usable.
Mainly as a test and mostly for the fun of it in the mid-late 90s was able to convert a 490-520 unit down to the 438-470 range by replacing parts taken from a carcass radio which consisted of over half a dozen low value (pF) tiny 0406 SMD chip caps mainly from the receiver stages and VCO, and possibly at a couple of other spots, plus having to swap the transmit power module, and then use the shift entry to program it. But in the end had somewhat limited success, as the radio basically worked but there where still some deficiencies and it would also not work properly for the whole intended new lower range. Maybe there where a few other caps that I missed, and in the end this non trivial procedure was barely worth the effort, but it proved that a range conversion was possible.
Hope that helps some.
