Tank repair

Ready to plastiweld my fuel tank , using an old fender for filler ... Any suggestions ? Tips ?
If I’m bonding two separate pieces I usually either super glue it first to hold it all in place while melting the different plastic together, or I may drill holes and use cable ties for the same purpose. I’m not sure why, but it seems if I cool it off with compressed air, the weld seems to be stronger. And no mater what you do, it’s gonna look ugly. Possibly sanding may help but it will look Frankensteinish either way.