There's a comment on the video about the instrument panel top warning light staying on. On my car, a 1999, the top light still functions normally. On my 2000 S that has everything including the top removed, the light stayed on until I jumped the connection:
On the 2000 - 2004 Boxsters the "Convertible top indicator light" on the instrument panel is controlled by a switch inside the left side roof transmission. You can make that light go out by jumping the Brown/Black wire to the Brown wire that connects to the roof transmission or just grounding the Brown/Black wire.
On 1999 and older the function is done by the "B-pillar switch". It should still operate normally after the top is converted to manual mode. The switch may be bypassed by jumping or grounding the wires to that switch.
Here's a thread that discusses that switch:
B-Pillar micro switch (98661310102)