I know what you mean have you used the billet front mount? I bought 5 of them and there great!!! only thing is there 1 1/2" and these damn astras have a 1.75" down tube go figure I remember by first bike I bought 5 yrs ago it was a cob job but I bought it anyways it took me 4 days to redo this guys work but when done the thing was nice I sold it a few months later and bought my first kit from e-bay. which is why im now selling these bikes they are addictive and boy is this high when there done GREAT!!!!!! love building them. im going to finally build my own now who sells the best bottom ends???? someone let me know.
In my experience tthe bottom ends that Duane/thatsdax sells have been the best Ive had, I havent looked in a few days, but he was out of them, bu5 may have some more by now, Im not saying his are better than anyone elses as far as other vendors who advertise here, but I have several other engines and none of them have as tood of balance as the lowers Ive gotten from dax, I have two of the newer 38mm stroke versions he's been selling lately, but I havent got one of them running yet to know how it compares to the 40mm stroke version he sold in the past.
I did call and talk to Duane before I bought them and he told me he had one built and going on a bike and the balance was just as good and he just cleaned the ports up on a jug, put a Puch head on it and use one of the Banana pipes and had got 40+mph with a 36T sprocket on the rear.
Thats really all I ever shoot for our of mine nowadays so I ordered two of the lowers, but my other projects have been taking up my time and I haven't had a chance to stick one together yet, im neexing to real soon though so I can give an honest review of them for those who may be interested.
Personally, I dont think you can go wrong by getting an engine or lower from Duane, hes a great fella who offers excellent service after the sale and thats important to me.