In conventional multibeam satellite systems, frequencyand polarization orthogonalization have been traditionallyemployed for mitigating interbeam interference. However, theparadigm of multibeam joint precoding allows for full frequencyreuse while assisting beam-edge users. In this paper, the performanceof linear beamforming is investigated in terms of meetingtraffic demands. More importantly, generic linear constraints areconsidered over the transmit covariance matrix in order to modelthe power pooling effect which can be implemented throughflexible traveling wave tube amplifiers (TWTAS) or multiportamplifiers. The performance of this scheme is compared againstconventional spotbeam systems based on the rate-balancingobjective. In this context, it is shown that significantly higherspectral efficiency can be achieved through beamforming, whileflexible power constraint offers better rate-balancing.