I have never tried a Drelinger headjoint. I would like to travel the 2 1/2 hours to the nearest city on his 'tour' next year to try some. This year I was too sick.
For an interesting article about one man's experience with Drelinger himself and selecting a headjoint, go to
http://voxflute.port5.com/drelinger.htm
If you are able, borrow a flute with a barrel large enough to accommodate the Drelinger HJ so that you can try it. If the HJ is really a steal of a deal, buy it and have it sized for your flute, and sell it if you don't like it. Before you buy it, ask a good flute tech to measure your flute barrel, and the Drel. HJ tenon, with a digital caliper. The tech can tell you if the HJ can be resized easily.
I always enjoy having a well made headjoint to try out. Very often it takes two or three days to really get the best out of the new headjoint. Even if you don't buy this headjoint, you will probably notice some 'new' things about your old headjoint. Those properties were always there, but you have learned new embouchure flexibility from the 'new' headjoint that translates to the old one. I attribute a lot of the improvement in my tone, and flexibility with different sounds on both piccolo and flute, to having, and using, two very well made, but different headjoints. (I have a Prima Sankyo NRS-1 silver headjoint and a Powell Philharmonic cut grenadilla headjoint.) I couldn't play the Powell very well when I first tried it, but now it is my favorite.
I take any opportunity I can to play a professional, handmade and well designed headjoint. For me, it is like getting free flute lessons.
<Added>Mr. Drelinger makes a LOT of different styles of headjoint, whereas many makers have at most four or five different headjoint cuts. Some people have compared trying Drelinger headjoints to Harry Potter's selection of a magic wand. What I'm trying to say here is that the headjoint that you have an opportunity to buy may or may not be to your liking, and the only way to know is to play it.