737-200 fuel planning
Kiwiguy...may not be able to give you the exact answer but did have 15 years flight planning 737-200 series aircraft for the major NZ carrier some years ago. Have dug into my personal aviation archives (don't ask why I kept these)....but may be able to fill in a few gaps.
At the time we planned to CAA rules (CASO 15) and not the annex for domestic flights. Initially we used flight planning tables but later on moved to a mainframe based system. Fuels below based on Pratt JT8D-15A.
Flight planning (assuming an alternate) consisted of
a) Pre-flight fuel (150kg - this gave 50kg for 30min of APU ops and 100kg for 5min start and taxi fuel)
b) departure fuel if required - calculated at 3min at 139kg if a 180 required after T/O
c) A-B fuel (this was from start of T/O to 1500ft overhead B)
d) 6% contigency fuel of A-B B/O
e) landing fuel - standard 135kg (3min)
f) instrument approach fuel - if straight in then 0 kg. If 'around the corner' 8min at 400kg, if straight in followed by missed approach and a second approach 15min at 770kg. if round the corner and a second go - 23min at 1170kg.
g) B-C diversion fuel
h) 3% contigency of B-C B/O
i) instrument approach fuel at C (as per 'f' above)
j) 30min holding fuel overhead alternate at 1500ft
k) where applicable a PDA allowance which was aircraft specific.
Holding speeds according to the book were 210kt clean. Don't forget the 250kt speed restriction below 10,000ft anyway. The tables I have indicated that at a ZFW of 38,000kgs then 30min hold equated to 1140kgs.
As a quick example I have an old computer fligt plan going NZWN-NZAA divert NZAA-NZHN which appears to be similar to your scenario. With a ZFW of 36300kgs at FL330 A-B calculated B/O was 44min at 1979kg (wind comp P010), B-C B/O was 17min at 887kg and alt reserve was 30min at 1146kg. Extra hold was based on 2400kg/hr.
I don't quite understand your inflight redispatch comment. You can divert to your alternate C on the way to B if you wish but this wouldn't affect your original planned fuel to go A-B. If you are planning A-C to reduce your fuel uplift that is a possibility but in the real world you might be embarrased if B suddenly opened. The other way you could get a bit more payload on departure is to use a higher flap setting eg flaps 5 or 15 instead of 1.
Cheers