It's a curious question because in B757/767 & 737 I tend to think of loss of height versus distance. For normal descents at 280kts and 250/100 then 170 as you intercept G/S the usual 3 x HT plus a few to slow down works.
Once at circuit speeds and assuming idle thrust:
210kts is roughly UP speed at common ELW. On a 3 degree ILS the speed will slowly accelerate: speed brake will just about hold it.
F1/190 will stabilise on G/S. F5/170 will do likewise, but selecting F5 will not slow you down from F1 speed. F10 will come down slightly steeper. Gear & F15 is about 2 x height in distance. F40 at Vref will just about do 1nm/1000'. Thus F25/30 will be in between 2x & 1x height.
A quick way to get down is F5 220kts & speed brake. This will also be about 2 x Ht. perhaps more. You then need to slow down 50kts which is best done in level flight and hit G/S o speed. I appreciate these are not FPA's, but they are useful in assessing distance required to lose height, which surely is what it is all about if you want to hit the correct crash point. As your grandma would have told you, "suck it and see." Use the same as B757/767 and adjust your datums. Always a good way to start. There's less inertia in B738 and like all slippery a/c it won't go down and slow down.