Combine Races with different LA

[adanger2u]

Okay, LA+10 max. World's largest Dungeon. Trying out ideas for races and thought of combining two races with different LA levels. All books are accessible.  The creatures I want to combine have different ages for each LA. One would be 26-50 and the other would be 16-25. I ran into that problem as well as the LA of 4 and  LA of 5 problem.  I figured I'd up the younger one by another age category and add another level of LA to it.  That makes them equal for age but the younger one was already the higher LA.  Now, I know this is going to seem crazy and that I'm deliberately trying to take advantage of a system someone else made up but I found a formula devised by someone else for combining creatures with the same LA. I then applied it to these two creatures.  Here's the link to the system I mentioned above.

http://www.giantitp.com/forums/showthread.php?t=276074

Using that along with some modifications to it. I tried to combine my desired races. The first is a juvenile Steel Dragon and the second is a young Silver Dragon.  The MM says that I can't play a juvenile Silver Dragon to start out but the LA for a steel young dragon is the same as the juvenile. I couldn't decide between the two so I tried to combine them. Now this was last night with a lot of sleepiness to it but I think it turned out alright.  I'm asking just in case this's something I can't do. There are many things that we "shouldn't do" but as PC we do anyway. I'm just wondering mainly if this is something I just can't do "properly". Since there's so many ways to "break" the game that I don't know about.

The ability scores are going to be rolled by me. I wasn't sure how to handle the saves so I left it blank, for now. I took the base attack bonus and averaged the two. I did the same with the natural armor. I wasn't sure how to handle the breath weapon so I just combined them, for now. I used the larger of the two for size of the creature. If you guys have any ideas on either how to make this work or just how to create a dragon as a PC. I'd really appreciate the help.

[adanger2u]

Here's some more circumstances involved with this decision.

I looked into the Steel Dragon as suggested on another thread as a race for a cleric and I really liked it so I looked at other dragons as well out of curiosity. The silver is quite similar to the Steel when it comes to feelings about combat and there's one of our fellow characters who won't be able to fly. Thinking along these lines I decided to make a dragon that could carry that character. I need the size of a juvenile silver even though the MM says I can't play as one right off the bat. Then I thought," What if I try to combine the two?""Can I combine two races?".  It helped that both can cast cleric spells like arcane spells.  So I looked up carrying weights and everything and found if I was a large dragon I'd be able to carry just about any other race easily enough as long as their gear didn't weigh too much.  So, I wanted the size of the silver at juvenile even though the book told me I couldn't play as it. I then asked the DM about something like this and he said that he'd leave it to my best judgment and as long as it didn't exceed the +10 limit I'd be allowed to create it.

Oh, I took the racial HD and averaged the amount the two have at juvenile age.  Silver has 16 and the Steel has 13. I averaged that then rounded down. With 14 HD I'd get feats for 1, 3, 5, 7, 9, 11, and 13. I then asked the DM about adding the Wyrm of War achetype to the dragon and if that would get rid of his ability to cast cleric spells as well as the sorcerer spells. He said he'd allow the dragon to keep the cleric spells since everyone else is ridiculous as well.

We have a dragonwrought-white dragonspawn-loredrake kobold sorcerer with the shadow templated added, a thri-kreen vampire , and and some ridiculous barbarian who's half minotaur and other things that i can't remember. All I know is that with a LA +10 limit everyone had great fun in creating their characters(other templates are probably going to be added to some of these).