Mounting large finder/gps combo

Hey guys, I am fairly new to this forum but from what I see there is most likely someone on that can help me with this. I have a 1198si Humminbird, I want to mount it in the dash of my 1850 tree. (Full windshield) I plan to use the “D” sized Ram mount. Can I use the short version? I an not at the lake where I can measure my boat.
Thanks for any help you can give.

See if this link works. The 1198 is heavy, this mount will NOT move under the weight.

https://rm.factoryoutletstore.com/cat/29855-110800/ram-mounts-flat-surface-horizontal-single-swing-arm.html?cid=443155&chid=4272&gclid=Cj0KCQjwyLDpBRCxARIsAEENsrJi6pDWw9oP9O2yJwlCgd12hRpQ5THwXSWHp-5B_aTVSYceOijs0TQaAtUaEALw_wcB

Thanks, that looks like a good option