Back to the OP - warming the tube in warm water will persuade it out of the tube a bit more easily but if you overdo the warming, it will cause the contents to go off.
The Sika range of products is expensive but they are MED and classification society approved and therefore attract a premium. If you don't need any of this then why not use a cheaper and possibly just as effective a product from somewhere else.
The Marine Flex looks quite good and at £4'ish a tube, it seems good value.
Unfortunately the down fall of adhesives and sealants tends to be in the preparation of the surfaces. If you use Sika 292i, which is their structural adhesive to bond together two dirty surfaces, it will be as effective as Blu-tack. If, however, you do the correct surface treatment using a primer if necessary then it will be just about as strong as the surfaces being bonded.
The Sika website is a mine of information on various bonding techniques.