Excellent choice! The lwd conversion barrel has been an excellent barrel for me! Not one failure of any kind! I would use it for SD and carry without hesitation. Ive had one or two issues with feeding with my stock barrel, pretty sure it was the ammo, but even still, technically, my conversion barrel is more reliable than my stock barrel!
Doubletap lies about their velocities, usually by 100-200fps, but it is still medium power for 10mm ammo. I, along with several others, absolutely refuse to buy from them though, because when the owner was confronted about the issues with his ammo hepretty much just said, "Ive got enough business to keep me busy, so why change?"
Underwood ammo is truly full power ammo, and meets or exceeds its velocities nearly every time! For the money, you can not beat Underwood! Buffalo bore also makes very hot ammo that meets its velocities, but it is very expensive, over a dollar a round typically. I would only buy buffalo bore if you had the need for a heavy hardcast round where a 200gr xtp, or fmj, absolutely could not be substituted...Hornady is another manufacturer whose ammo consistently meets its published velocities, however it is only medium power ammo, in spite of this, their 155gr xtp is still an excellent carry round, IMO.
As far as mods go, shoot it before you change anything, you may be surprised and really like it! However I felt like the trigger could be improved, and since I would mostly be shooting very hot ammo I knew I needed a heavier recoil spring to reduce battering of the gun, and keep my brass from flying 25 feet away. So here is a list of mods I did to my G20sf:
LWD trigger overtravel stop
Ghost 3.5lb connector
6lb trigger spring
ISMI 22lb recoil spring on a SS LWD guide rod
XS Big Dot 24/7 Night Sights
Chrome pin kit with extended slide release from rockyourglock.com
I use Ballistol to clean and oil it, Ive been very happy with it. Just a little advice in case you dont already know: make sure you coat the inside of the barrel (and anywhere else that may get dirty, like the feed ramp) with oil before you shoot it and every time you clean it. This will make cleaning the barrel a whole lot easier after you've shot it!
P.S. Be sure to check out the 10 Ring forum here, its under the "Gun-Related Clubs" section. Lots of good guys and good info!!! And, if youre a reloader, there is a reloading forum here totally dedicated to the 10mm!