Just a little more info about map regions on 27x0 devices. There are 4 of them as far as i recall:
region 3 (hex 0x03) for the basemap;
region 10 (hex 0x0A) for a supplementary map otherwise known as gmapsupp.img;
region 49 (hex 0x31) for the original factory entitlement detail map otherwise known as gmapprom.img;
and finally
region 50 (hex 0x32) for a (sometimes) factory-loaded small info map otherwise known as gmapoem.img.

Note that gmapoem.img is not always present in rgn50 and if it is, it's meant for dealer location POIs in branded devices Garmin makes for BMW, HD, Honda etc.. In any case, rgn50 usually has a quite small space allocation although it actually shares space with rgn49 so removing an OEM map makes a little more available for a primary PROM detail map. However, rgn10 has its own dedicated space for a secondary SUPP detail map. The region-layout does differ in these older non-MSM devices like SP and GPSMAP devices however and i'm going from memory about 27x0. Regardless, i don't think you'll have enough space on your 2720 allocated to rgn50 to flash a detail map of any size and a new primary detail map will need to be flashed to rgn49.