If you have a huge, aftermarket coil, I'd offer up for sale portrayed and hopefully find somebody who thinks they are going to benefit from having an oversized coil.
I have eight detectors in my personal outfit and only one of them has a bigger size coil. That's my Garrett Apex with the 8-1/2X11 'Raider' DD. Coil mounted for open-area searches. All the rest of them have a small or mid-size coil mounted. For five and a half decades smaller to mid-sized coils have served me quite well, and a lot of that was early-on when I was healthier and had ample mobiluty. Today, it's a different. I've been getting around with a cane for just over 28 years and with other compounded help limitations my getting down and getting up is a serious struggle both ways.
Most of the good targets I find now are between surface and 5" or 6" with the few occasionally down to 8". Things haven't changed much since I got started in '65 .... most good stuff is surface to 4" and in some of those a little bit deeper fall into that depths up to give or take 6".
I enjoy using both my Bandido II microMAX and Silver Sabre microMAX with their 6" coils, my Relic w/5" DD, Simplex + w/5X9-1/2, ORX w/5X9-1/2 HF, and Apex devices w/5X8 'Ripper', the above mentioned 'Raider' coil, and a NEL 5" DD.
I also like all of my simple to easy-to-use detectors because I don't care for complexity.
I wish you the best of success on every opportunity you have to get out detecting.
Monte