/*
* Cost Comparison of different ways of stacking fusion reactors.
* Calculations made with crafting recipes in v3.04c of Gregtech.
* Last Edit: 7th May @ 14:55
*
*/

Report miscalculations @ http://tinyurl.com/btzvlyg
***

TLDR: skip to the end for the best setup, which is not shown directly below.

Horizontal Stacking - Saved Resources:
3x Coil
16x Advanced Casing

Vertical Stacking - Saved Resources:
32x Advanced Casing

We can take 16 advanced casings from both to reduce it to:

Horizontal Stacking - Saved Resources:
3x Coil
0x Advanced Casing

Vertical Stacking - Saved Resources
16x Advanced Casing

===

Not: Costs are calculated with version 3.04c of GregTech.

Cost of 1x Fusion Coil
 - 4x Energy flow circuit
  - 4x Advanced Circuit
  - 2x Tungsten Plate
  - 1x Iridium Plate
  - 2x Lapotron Crystal
 - 1x Superconductor
  - 3/4x 60k Helium Coolant Cell
  - 1/4x Iridium Plate
  - 1/2x Tungsten Plate
  - 3x Energy Flow Circuit
   - 3x Advanced Circuit
   - 3/2x Tungsten Plate
   - 3/4x Iridium Plate
   - 3/2x Lapotron Crystal
 - 1x Highly Advanced Machine Block
  - 4x Chrome
  - 4x Titanium
  - 1x Advanced Machine Block
 - 1x Iridium Neutron Reflector
  - 8x Berylium Cell
  - 64*2x Coal Dust
  - 32x Dense Copper Plate
  - 1x Iridium Plate
  - 2*64x Tin Dust
 - 2x Nichrome Heating Coil
  - 1x Chrome Ingot
  - 4x Nickel Ingot

Cost of 4x Advanced Casings:
4x Advanced Casing
 - 6x Chrome
 - 1x Highly Advanced Machine Block
  - 4x Chrome
  - 4x Titanium
  - 1x Advanced Machine Block
 - 2x Data Control Circuit
  - 2x Data Storage Circuit
   - 4x Emerald
   - 1/2x Advanced Circuit
  - 1/2x Iridium Plate
  - 4x Advanced Circuit
---

Cost of 16x Advanced Casings
22 Chrome
16 Titanium
4 Advanced Machine Block
32 Emerald
37 Advanced Circuit
4 Iridium Plate

Cost of 3x Fusion Coils:
21 Advanced Circuit
12 Tungsten Plate
9 Iridium Plate
21/2 Lapotron Crystal
9/4 60k Helium Coolant Cell
15 Chrome
24 Titanium
3 Advanced Machine Block
24 Berylium Cell
384 Coal Dust
768 Copper Ingots
384 Tin Dust
12 Nickel

---

There's another setup, which I call the Overlapping Horizontal Stacking. It can save you 4 fusion coils & 23 advanced casings.

It's built like this (screenshot of just the first level):
http://i.imgur.com/34YPTNM.jpg

Source of screenshot: febcad @ http://tinyurl.com/bsfvexs