those jump jets are actually by the book :) i was, and still am, surprised myself. btw, difference in weight you were experiencing is from 3 tons heavier engine and 0.5 ton heavier structure on Shadow Hawk, which gives only 1.5 tons more free weight than Trebuchet.

Just click 'reply' on a post, and see what shows up in your formatting popup.

oooh, so simple ^^ thanks a lot

realised i never marked any post as the answer to my question, while some posts here held the start of an explanation, though i had to dig up on my own side a little as well:

mostly, from what i understood (thanx to some leads given here), the difference of free tonnage on two same size/total tonnage mechs is engine related.

i discovered that all naked, or with same set of loadout, the trebuchet would have a better movement range than, lets say for the example, the centurion

so i assumed some mechs within same tonnage category and same exact max tonnage had more or less powerful engines, allowing greater or lesser movement distance per turn.

now something funny is that the trebuchet, one that is initially designed as a backliner artillerye LRM based mech can actually move faster while it doesnt need to mode much at all, while centurion which may be better in front line and is more polyvalent/less specialized in its possible loadouts due to his available weapon hardpoints diversity and placement... ends up being the most sluggish one regarding base movement rate.

which led me to the conclusion that centurion was better put at backliner role of, supposedly, the trebuchet, and trebuchet was in fact more useful if refitted as a frontline attacker with short range weaps such as srm, and melee charge... go figure :)

Thanks for the insight, you all...

The main reason for long-range mechs to have greater speed is so that they can maintain that range. Being slow means that you can be caught by the close-range specialists, and then you're in real trouble.