Cleon
Legend
Let's go with Str 15, Dex 13, Con 14, Int 4, Wis 12, Cha 9 and Dex poison, then. Dex 13 gives us a few more feat options.
That's true. Opens up the Dodge tree, among others.
OK, we seem to be getting somewhere. Good point about the Feat prereqs. So, we're agreed on Str 15, Dex 13, Con 14, Int 4, Wis 12, Cha 9.
As for the poison, I'm still against plain Dex damage. The description says it only causes slowness as its initial effect, if it does Dex it (a) has the potential of causing paralysis and (b) has a lot of fiddly knock-on effects to its target's stats. Some status effect seems both simpler and truer to the original to me.
What about its other stats. I'm seeing something like the following:
Hit Dice: 5d12+10 (37 hp)
Speed: 40 ft. (8 squares), fly 60 ft. (poor) [Faster on land, fly = Wyvern]
Armor Class: 17 (+1 Dex, +6 natural), touch 11, flat-footed 16
Base Attack/Grapple: +5/+7
Attacks: Sting +7 melee (1d4+2 poison) or bite +7 melee (1d10+2)
Full Attack: Sting +7 melee (1d4+2 poison) and bite +5 melee (1d10+2)
Special Attacks: Poison, improved grab [Like a Wyvern]
Special Qualities: Darkvision 60 ft., immunity to sleep and paralysis, low-light vision, scent [Like a Wyvern]
Saves: Fort +6, Ref +5, Wil +5
Abilities: Str 15, Dex 13, Con 14, Int 4, Wis 12, Cha 9
Skills: Hide +9, Listen +9, Move Silently +9, Spot +9, Survival +9
[Like a Wyvern with Survival as the extra skill from its higher Int, all maxed out and not including any feats or racial bonuses it may have]
Feats: Two, plus Multiattack (B) [Multiattack as a bonus like Wyvern]
Environment: Warm hills [Like a Wyvern]
Treasure: Standard [Like a Wyvern]
I'm thinking one of its feats should be Alertness, since both the Wyvern and Pseudodragon have it, and probably Ability Focus (poison) for the other.
As for Advancement, Wyverns have an odd advancement, being 7HD (Large); 8-10 HD (Huge); 11-21 HD (Gargantuan) so I'm thinking something similar for the Bloodstinger, how about:
Advancement 6-7 HD (Large); 8-15 HD (Huge)