making a rack doesn't have to be frustrating,back heat is a bit easier to install (i believe this is the reason many mfg.'s use it,less labor intensive in a competive market) but more expensive and less efficient.
for example my last rack is 10 level 41qt. sideways tubs.i use 3" 6 watt heat tape belly heat,this runs less than 180 watts for the whole rack.if i were to slap 11" heat tape on the back it would be about 300 watts.keep in mind this runs 24/7 plus if you plan on getting into mulitiple racks you will have to purchase more thermostats.if you try to heat a 41qt or cb70 tub from the end with back heat it simply is not efficient.
hope this helps!