We've all seen them, the quill convertors that allow you to install a threadless stem on a threaded fork. I have an old Burley tandem that will be a compromise between two height extremes. I figured it was probably better for me to be raised up higher
and extended out front a little, than the stoker being on too tall of a bike. Plus the bike was foud that way. Are these considered
fairly safe? I need a good 3-4 inches of rise to put the bars where I need them, and I have a nice 115mm threadless stem that will put me about where I need to be. I want to run drop bars about level with the saddle for long distance comfort. To give you an idea of what I am up against, here is the bike in as found condition, with the saddle up front at the height I need it for correct leg extension. Maybe I should drop the cash for a technomic deluxe and call it a day?,,,,BD

Forgive the condition, it is a recent acquisition, and will get the full treatment.