IIRC the Stampede uses same esc as the Slash and the Novak Smart Stop lvcs do not work with the stock esc. I haven't seen anyone report the CellPro lvc works one way or the other. Most that are running lipo have either upgraded to BL or are racing where the run time is such tha the lipo isn't overdischarged.

The safest thing to do would be for him to get a NiMH pac for his 4 yr old to run. Thats the only batt thats going to be safe in this situation.