Are you using the skimmer box for the remora? The box measures 8.5" x 7.25" x 2.5",(for the MJ1200 units) so you may be constrained to that size if you are using the box.
I thought I needed a bigger pump than the 1200 with my remora...cleaned it with vinegar/water, and it skims just fine (noticeably better in fact). If I keep up the maintenance on it I've been able to avoid the Mag3 so far.
i think the mag series pumps get somewhat of a bad rap here.
i do agree with the screw issue(looking for plastic ones).
but there are workhorses.
i run mag 7 return and a mag 3 on the remora pro
total watts maybe 100.
i have a 25 aga and 15aga(90% full) along with a Sunpod, my room temp runs between 72-75(old condo) more in summer. i never have a problem with heat during the summer i run a fan no chiller.
temp in winter 78-79 , summer 79-81