[Jack Simth]

Well, I was actually hoping Alneyan would show up at yesterday's session, but that obviously didn't happen; the plan would have been for him to show up at the recruiting station at the same time as the party; ah well.

A Wyrmling Silver Dragon has a level adjustment of 4 and seven racial hit dice - ECL 11. Combined with your 13 Rogue levels, that would have to wait until ECL 24.

Seriously, though - what benefits are you missing? You apprear to be reading the feat entry incorrectly; they don't get a bonus feat, they get character level feats based on their hit dice - one at 1st and one additional feat per 3 hit dice - hence the 45 HD example Force Dragon in the Epic section having 16 feats; "just like any other creature." You already have all the special abilities listed for the Wyrmling (Alternate Form, Immunity to Cold and Acid, Vulnerability to Fire, Cloudwalking); the Spell-like abilities don't start until Adult stage, they don't get a Sorcerous caster level until Young, and no SR until Young Adult. Your BAB should now be +10 (over the Wyrmlings +7); your attack bonus of +12 (+10 BAB, +1 Size, +1 Strength) is over the wyrmlings +9; your Grapple check is correspondingly higher (+7 vs. the Wyrmlings +4); your current saves of +7/+10/+7 beat the Wyrmlings +6/+5/+7; you have the same breath weapon (at a higher DC), the same flight speed, the same inherent natural armor, and the same size bonus to AC; in addition, you have lots of equipment that raises your AC even more; you have a great many more skill points from your Rogue levels (rogue gets 8+Int Mod per level, while dragon gets 6+Int Mod per HD). Okay - so your Wisdom and Charisma are a few points lower - but that could easily be passed off as simple random variance.