Since we are talking about 1/4" tape drives

There are a lot of unknowns so, this may be a hard nut to crack but, I'm having problems. I am trying to revive my old AT&T 3B2/600G and I need to re-install the os. It has a 120MB tape drive and I have an image of the install tape. Thing is the tape drive's capstan turned to liquid long ago. Typical Wangtek. I have five here with melted rubber all over. The drive is a AT&T badged 5125ES scsi drive. From what I read they will read 60mb format tapes but, not write them. They read/write QIC-120 and nothing else. The drive actually id's as a wangtek ks23465 which is a at&t part number and probably messes up the drivers from knowing what it is. Anyway, I took the capstan out of a wangtek 5250es drive I bought off ebay and put it in the 3b2 drive. Then I put it on both a solaris and linux box. The problem I am having is, while it works fine, it uses way more tape than normal. A 4mb file uses about a half of a dc600a cart and about the same for a 6150. I can't fit the boot tape on a tape. Not even close. Maybe four files and I have 37. I've tried using various tools to set the density but, the drive just gives an i/o error if you try. While I do have a few 6150 tapes I don't have an actual qic-120 tape. My understanding is a qic-150 tape should be fine for qic-120. So, could the capstan rubber be different enough to cause it to eat up more tape or is it a driver/firmware issue ? The rubber looks about the same as every wangtek one I've ever seen but, it's softer than I remember them being. I have tried setting up solaris and linux with the device name but, I think there are special characters in the id string and I can't get either os's drivers to id it on boot. The commands like probe-scsi give a lot of strange spaces after and before parts of the device name as reported by the drive.