While I have no experience on dumping final sectors, and my short checking experience ex-LHR is a little bit different than what you are asking, I thought I might share anyway

LHR staff were OK to short check my bags to KUL even though I had 1hr 45min layover in KUL. Realistically, if the pax was thinking of clearing immigration, picking up the bags and checking them in again 60 min. before dep. I'm not sure anything less than 2 hrs is enough. I had told the LHR staff that I would be picking up my bags and taking them on as carry on.

However, my intention was to leave them at left baggage at KLIA while I continued on to HKT, doing the turnaround and back to KUL the same day. I did make sure to stop by the trf desk at KLIA to inform them that I had a turnaround & without even pulling out my booking in their system, the staff just said that my bags will be kept at the lost & found office.

Well, I guess since no one informed the baggage office that I was doing a turnaround, they collected my bag & tagged it to HKT with me on my flight! So when I came back to KUL in the afternoon, and went to the lost & found office, the guy at the office told me my bags were still in HKT!

Anyway the bag was delivered to me in KL 48 hrs later, along with RM250 in compensation for delayed bags which I am to collect from the KLIA office on my next trip to KUL later this month. I also filed a claim with my travel insurance company with all the airline reports. Waiting to hear back from them how much comp I am entitled to