If you've ever seen the pornstar Shorty Mac in action, you'll have seen that not many women can take him all, blowjobs are limited to sucking his glans - he is only about 3/4" thicker than your maximum girth!!!
Huge girth starts at 6", you really don't need any more girth (unless you hate blowjobs)! An extra inch or 2 in length wouldn't hurt in your case I think.
Try this for extra length:
Warm up your shaft for 5 minutes with a hot rice sock or a flannel soaked in hot water (when the water cools rinse and soak with more hot water)
Make sure that your penis is between semi-erect and floppy (30-50% erect) whilst you jelq, if it gets hard, stop and wait for it flop. Jelq using the jelq device for 10 minutes to start with, at the end of each stroke hold it stretched for a few seconds and repeat.
2 days on and one off, add 1 minute each week.
However if you want to limit your sexual potential and add some more girth:
After a 5 minute warm up, jelq at 50-80 percent erect, each stroke should take around 5 seconds. Do this for 10 minutes to start with, 2 days on and 1 day off. Add an extra minute each week.