So the control points you stated above are not definite. LDraw-mode will move the first control point forward and backward along the line composed from the first end point, and similar with the second, to achieve the length you specified. But the ratio of the distance from the first control point to the first end point and the second control point to the second end point is preserved. If the distance between the first end and control point is the larger, the effect of the hose being less flexible in that end is simulated. This is probably only rarely needed, so you'll usually want the ration to be one.
Some variables control how the numerical integration works.
Eight is the default, which is probably more than enough unless you have few segments and much curvature. If you're modeling a very short curve, you may want to lower this number. If the length of the curve LDraw mode comes up with is too short or too long compared with what you originally wanted, you can try to increase this number to overcome the problem. The first axis in the rotated coordinate system should be perpendicular to this vector. Try to alter this vector if you experience weird twisting of the curve.