QUOTE
An explosive's Damage Value is calculated as (modified) rating x the square root of the kilograms used.
Instead of planting a 5kg charge, with rating * 2.2 DV, why not plant 5 1kg charges? Then there are 5 attacks of DV = rating * 1, the only downsides are that it takes longer to plant and the separation of attacks means you can't just edge once.
The second question applies to planting explosives on large barriers. The rules imply you keep a damage counter for each 1sqm area of the barrier.
QUOTE
The Structure rating is the number of "damage boxes" required to destroy a section 1 meter square and about 10 cm thick)
If you detonate one explosive charge on a barrier, but the damage is insufficient to "make a hole", you then track the blast effect out until the damage diminishes to 0. You can then apply charges anywhere on the weakened areas to finish them off. Damage in excess of the "structure rating" remaining spills over to adjacent squares. Does this interpretation look right?