OK, did a little playing with Excel
I generated cm by multiplying the height by 2.5
the Base Scale Multiplier is multiplied by by the scale found in the [2DPatternWindow->Scale Up/Down Development By Specifying Value...]
If the value already in that box is 30.342, you can use the value in the last column
These are only starter values, some parts may need to be scaled differently to make them fit right. You might also want to go two sizes up, if you use your exact height, the armor will be your height (from base of boots to top of helmet and won't fit around you)
Don't apply these to weapons; in general, weapons have a set size. One exception, you want to make your child look like he really is the master chief you can try using the Base Scale Multiplier to do so, but you're going to have to get the weapons to full scale first (or find some pdos that have already been fixed)
Why did I stop at 12 inches (30cm)?
Hey, why not make a set for your 1ft GI Joe (or just make a desk display)
(some of those folds are going to be d@|V|3|) hard to make)
Height---cm-------Base Scale Multiplier-----If current scale is 30.342
78-------195-------0.906976744--------------27.51948837
77-------192.5-----0.895348837-------------27.16667442
76-------190-------0.88372093---------------26.81386047
75-------187.5-----0.872093023-------------26.46104651
74-------185-------0.860465116-------------26.10823256
73-------182.5-----0.848837209-------------25.7554186
72-------180-------0.837209302-------------25.40260465
71-------177.5-----0.825581395-------------25.0497907
70-------175-------0.813953488-------------24.69697674
69-------172.5-----0.802325581-------------24.34416279
68-------170-------0.790697674-------------23.99134884
67-------167.5-----0.779069767-------------23.63853488
66-------165-------0.76744186---------------23.28572093
65-------162.5-----0.755813953--------------22.93290698
64-------160-------0.744186047--------------22.58009302
63-------157.5-----0.73255814---------------22.22727907
62-------155-------0.720930233--------------21.87446512
61-------152.5-----0.709302326--------------21.52165116
60-------150-------0.697674419--------------21.16883721
59-------147.5-----0.686046512--------------20.81602326
58-------145-------0.674418605--------------20.4632093
57-------142.5-----0.662790698--------------20.11039535
56-------140-------0.651162791--------------19.7575814
55-------137.5-----0.639534884--------------19.40476744
54-------135-------0.627906977--------------19.05195349
53-------132.5-----0.61627907---------------18.69913953
52-------130-------0.604651163--------------18.34632558
51-------127.5-----0.593023256--------------17.99351163
50-------125-------0.581395349--------------17.64069767
49-------122.5-----0.569767442--------------17.28788372
48-------120-------0.558139535--------------16.93506977
47-------117.5-----0.546511628--------------16.58225581
46-------115-------0.534883721--------------16.22944186
45-------112.5-----0.523255814--------------15.87662791
44-------110-------0.511627907--------------15.52381395
43-------107.5-----0.5-------------------------15.171
42-------105-------0.488372093--------------14.81818605
41-------102.5-----0.476744186--------------14.46537209
40-------100-------0.465116279--------------14.11255814
39-------97.5------0.453488372--------------13.75974419
38-------95--------0.441860465--------------13.40693023
37-------92.5------0.430232558--------------13.05411628
36-------90--------0.418604651--------------12.70130233
35-------87.5------0.406976744--------------12.34848837
34-------85--------0.395348837--------------11.99567442
33-------82.5------0.38372093---------------11.64286047
32-------80--------0.372093023--------------11.29004651
31-------77.5------0.360465116--------------10.93723256
30-------75--------0.348837209--------------10.5844186
29-------72.5------0.337209302--------------10.23160465
28-------70--------0.325581395--------------9.878790698
27-------67.5------0.313953488--------------9.525976744
26-------65--------0.302325581--------------9.173162791
25-------62.5------0.290697674--------------8.820348837
24-------60--------0.279069767--------------8.467534884
23-------57.5------0.26744186---------------8.11472093
22-------55--------0.255813953--------------7.761906977
21-------52.5------0.244186047--------------7.409093023
20-------50--------0.23255814---------------7.05627907
19-------47.5------0.220930233--------------6.703465116
18-------45--------0.209302326--------------6.350651163
17-------42.5------0.197674419--------------5.997837209
16-------40--------0.186046512--------------5.645023256
15-------37.5------0.174418605--------------5.292209302
14-------35--------0.162790698--------------4.939395349
13-------32.5------0.151162791--------------4.586581395
12-------30--------0.139534884--------------4.233767442
Remember, these are starting points, test fit your armor before continuing with fibreglassing or using as a template for plastic or other materials
Hope this helps!