Transitions between Outside Fighting to Inside Fighting?

I've been rather confused when it comes to doing combinations that involve bridging the gap between Outside Fighting range to Inside Fighting range. I know this question sound very basic and rudimentary, but I'd just like conformation and advice.

For example, let's take the 1-2-3 (Jab, Cross, Left Hook). You move in with a Jab, land a shorter right, and emphasize the Left Hook at the end right? I always want to throw all three punches at their full extension, instead of shortening one up to land another one.

Another example is 1-2-3b-3 (Jab, Cross, Left Body Hook, Left Head Hook).

I always feel like with all these combinations, I want to throw the Cross that links the the Jab and Left Hook together at the end at full extension. Is this wrong, should I shorten the Cross (throw a shorter Cross) to land the Left Hook? Or should I throw a shorter punch (like an Overhand Right), instead of throwing the Cross, which is longer?

I might be majorly over thinking this, but it has left me very confused. Any advice would be greatly appreciated, thanks!

Sorry for the late reply but i just came across this post.
What i normally try to do with this combo when trying to close the distance is with the jab take a little half step forward/left which opens up my stance a little and will give me a slightly wider base so that i can throw a nice short right hand followed by a more powefull left hook.
Like you said if you were to throw the right hand to full extension then this would push youre opponent to far away from you,So this is why i try to keep the right nice and short but you should also find that this makes for quite a powerfull right hand.
This is not really something i have been taught however more just something i have picked up from watching others,So would be interesting to hear others opinions.

I havent got much time but to get straight to the point i would throw all three with good balance proper bio mechanics with decent weight transfers on all three punches, the point in throwing any combination is to land a punch or maybe a few of them, so if your strauight right hits and pushes your oponent back i dont see that as a bad thing really, if this happens and you hit your opponent or he falls back then forward shift on him for the left hook or maybe use a left straight by basicaly stepping forward with the punch with your right foot putting you in a southpaw stance when you land the hook or left cross. or maybe try stepping forward and to the right with the left hook. hope this helps

Maybee try watching clips of tyson on the heavy bag he usually throws quite a short right hand while moving in for the left hook.
I actually asked a similar question a while back concerning the footwork with the 1,2,3.

I think a short right hand can be a very good shot to throw when moving in on youre opponent,You still throw the punch with proper technique the only difference being the extenstion of the arm.
Bernard hopkins also throws a nice short right hand.theres some good clips on you tube of him throwing this type of shot on the mitts.It's a punch that results in a lot of knockouts probably because the opponent often dosent see it coming and has less time to react compared to say a long rangey right cross.