[alexrom1207]

Bungie strap will not work well at all, once you switch to the surgical tubing you'll find a much quicker and smoother pull than the bungie. On the subject of carbon fiber, the weight will make the spear basically useless, and the nature of carbon fiber is that it is very rigid and will snap and crack if bent too far, making it a horrible material for a spear.
On the fin issue. Split fins work really well for scuba guys because the tank and bc etc... provides much more resistance than a freediver. So the split fins allow some of the propulsion of the kick to dissipate (hence the water lost when the fin flexes and splits) when the load they are trying to push is too much. This prevents the diver from forcing his way forward and essentially plowing through the water and using up all his energy. This is the reason they feel easier. A freediving fin will not allow that energy to dissipate and for a scuba guy will not really move him faster because it just plows him through the water creating more resistance. Since freedivers are more streamlined they can afford to move faster and don't need a split because the fin flexes when the load increases and that is enough to prevent them from tiring themselves out. But stronger and heavier guys want stiffer fins because a soft fin will flex too soon for them and prevent them from reaching their optimum speed/distance at a reasonable kicking speed.
In the end, skindiving fins are just fine for shallow dives ( I used them for years and years). They are easier on the surface, easier to maneuver with, and will splash less when you dive down an angle (therefore scaring less fish away). I recently got some cressi gara 3000ld freediving fins and there is quite a difference in speed and distance. Leisurepro.com has them cheap if you ever decide to upgrade. But for starting out skindiving fins are a much less expensive and easier way to get started.

Happy hunting