transmission guys, need a little help

this hasnt come up in a while, but i need some guidance.

im having a 1-2 shift overlap issue. Ive adjusted the front band to a couple different specs (2 and 2 1/2 turns out) but it is not helping. what im looking for is a step by step instruction on what i need to do to get rid of this , or at the very least minimize what is happening before i jack something up. pics would be invaluable. ive searched youtube and i cannot find any info dealing with this exact problem. this car is my daily driver so pulling the trans is not an option (unless i break it) and im not looking to buy a shift kit (unless i have to), only to remedy the problem. im hoping to pull the pan off only once and get it right the first time, unless there is a way to do this without pulling it off at all.

a little background. this is a 67 727 that is behind a stock 318 out of a 67 coronet. i have never had the pan off and i am assuming it has been rebuilt and has factory internals with no shift kit. im also assuming it has an 11" converter. the fluid looks, smells and tastes (lol) normal and is exactly full. this trans never slips or makes any unusual noises and does not leak. i am using 2 quarts of type F mixed with Dex 3 of which is 2 years old and looks fresh . the fluid that was in it was very good. the trans works great under normal operating conditions, it does not "bang" gears, although when i get in to the four barrels, it will get a 1-2 bark on pavement when the shifter is in drive, also, when i put it in drive, it shifts through all the gears like it should, downshifting and upshifting very well and feels as though it is working properly. when i take off in first gear and attempt to manually shift it into second gear, it bogs down for about 3-5 seconds before it shifts and second is sluggish to get going and feels like it is not completely getting out of first gear when second engages. this REALLY bothers me and im not trying to burn up this transmission. 2 -3 shift is great. i have stopped taking off in first altogether and i only use drive. will this trans eventually self destruct ? or is it OK to use it with the shifter in drive? i really need to fix this as i have been attending to other areas, but now its time.

ive heard of some kind of accumulator or servo mod that can fix this , but i have no idea where to start. i am a novice when it comes to transmission internals, but im sure this is nothing i cant handle.

sorry for the long winded post , but im trying to be as clear as i can. thanks in advance , i really need some good, clear instruction here. :D
Lance