the tacks are just tacks. if ur goin for cosmetics just strike ur torch and run over them with out the rod. it will suck it back to match the rest. just strike up then lift ur hood up and watch from the inside. itll start turnin colors then itll get white and start to suck back. just walk the cup like ur runnin a hot pass sorta. and no its not ok to run down hill. ur talkin bout on ur off side u want to run down hill wit ur good hand. (prob ur right hand) u gotta learn to use ur other hand. (prob ur left hand).

Reduce your current.

Best regards - Al

are you practicing with tube coupons? Or actually in a boiler repairing tubes? Tube welding is actually easier then you think, tubes dont need 4 tacks on them, at least I never put 4 on them, 2 at the most and you weld it in pairs, do 1 half, then the other half. your usually running so fast that when you stop after your first half you can look inside and make sure its ok before you do the other half...most of the time it doesnt draw to bad....now if you have to take a "tube" test for a company, put your 4 tacks in it, if that makes you more comfortable and just feather down your bottom, top and one of the side tacks, this will help you keep at a moderate speed and help ensure that you make a consistant root....also the make these neat tube pliers that rotate so you dont even have to tack your tubes...I'll find the brand name and send it to you. also, tig ties in better uphill.....also, I never gap my tubes...there so thin that they are fusing together when I lay my rod on the bevel....but to each his own.